Aquarium maintenance tips and fish care guidelines

Neon tetras in clear water freshwater aquarium

Good aquarium maintenance practices will lead to a healthy aquatic environment and thriving fish, providing years of joy for the hobbyist.

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Expensive and time-consuming problems can be prevented by spending thirty minutes on maintenance every other week.

The biggest factor for maintenance is tank stability. As long as everything is running properly and your fish are healthy, there is no need for any major change, even if the pH or hardness seems to be slightly out of range; only increases or decreases of the major aquarium water parameters will need your careful but immediate attention.

Water Changes

A key part of aquarium maintenance is the water change, which should be performed about every two weeks. In most cases, 10-15% of the tank volume is sufficient. A good method is to replace the water extracted while vacuuming the gravel, which will eliminate uneaten foods and other residues that settle on the substrate.

It is highly recommended to check the water parameters of both the tank and replacement water. Most tap water (city water) contains either chlorine or chloramine. Chlorine will air out rather quickly (kept in an aerated bucked for twenty-four hours); chloramine (chloramine = chlorine + ammonia) will not. Using a water conditioner will neutralize the chlorine in both cases, but ammonia will still be present in the latter. It has to be broken down by the nitrifying bacteria present in the aquarium. This may take longer than your fish can tolerate.

Other elements of municipal water may be phosphates, iron, and other heavy metals. To find out about your tap water chemistry, call your local water company.

Well water is usually harder than tap water, but is chlorine/chloramine free.

Filtered water should also be checked on a regular basis and should be considered part of your aquarium maintenance routine. The filter membranes could be damaged or may require replacement prior to the expiration date.

Testing Aquarium Water

Water chemistry is not visible; therefore, it is vital to check it on a regular basis. The best way to make this a routine is to check on the tank chemistry while changing the water.

The vital parameters are pH, nitrates, nitrites, and carbonate hardness (salinity for marine tanks).

Stability is the main factor with pH. pH in the range of 6.5 – 7.5 is suitable for most species, but they can adjust if slightly out of range.

KH (carbonate hardness) is the indicator of pH stability. It should be kept under close observation if it comes close to 4.5 dH (degree hardness) or 80 ppm. You must take action if it decreases any further.

Half a teaspoon of baking soda per twenty-five gallons of water will raise the kH by about 1 dH (17.8 ppm).

Nitrites should be undetectable at all times (except during cycling). If you detect nitrites make sure you check on ammonia as well.

Nitrates should be kept below 10 ppm in freshwater and 5 ppm in marine and reef (preferably 0 ppm).

Aquarium Filtration

The proper function of the filter is essential. Filter inserts (floss, Algone, activated carbon) should be changed at least every four weeks. A high fish load may require shorter periods. Trapped particles will decompose in the filter as they would in the tank. The filter should also be cleaned once a month (do not touch the bio-wheels, if present) by using the water extracted from the tank during the water change.

Recommended Aquarium Maintenance Routine


  • Make sure the equipment is running properly.
  • Watch your fish during feeding. Behavioral changes are a good indicator of a potential problem.


  • Count your fish. In case of fish death, smaller species can decompose quickly, resulting in ammonia and nitrite spikes, and eventually high nitrate levels.

Every Other Week

  • Test your water for the vital parameters: pH, carbonate hardness, nitrite and nitrate.
  • Change 10-15% of the water .
  • Vacuum the gravel .
  • Clean the aquarium walls. Filter floss is fairly cheap and very efficient. Start from the bottom upward and rinse out often.
  • Rinse filter inserts (cartridges) with the extracted water.


  • Replace filter inserts, cartridges, floss, carbon, and Algone.
  • Inspect tubing, connections, airstones, skimmers and other parts for proper operation.
  • Clean aquarium top to assure your lighting is not affected.
  • Check the expiration dates printed on the boxes and bottles of the aquarium supplies you use. Do not use after the imprinted date. Expired test kits will give false readings and may prompt you to take unnecessary action.

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134 thoughts on “Aquarium maintenance tips and fish care guidelines

  1. Tony says:

    I have some freshwater plants and on the end of one of the leaves there is a worm looking thing that Sprouts clear hairs into the water kind of looks like it’s feeding off the water it almost looks like a saltwater reef plant

    • Thilo
      Thilo says:

      That is likely beard algae. You can remove the leaf, or if the algae has progressed, give the plant a bleach bath (1 part bleach 9 parts water) for about 5 minutes. After that, give the plant another bath, this time just water with conditioner. This will remove any bleach residues.
      The likely cause for the algae is low CO2 levels. You can read more here

    • Thilo
      Thilo says:

      It could be mold or algae, in either case it can be cleaned off very easily. Just remove the air stone and clean thoroughly, rinse in clear water with conditioner before placing it back in the aquarium.

  2. Desiree Curry says:

    I have 5 fish and a algae eater in a 53 gallon tank. Every two days the tank is a cloudy green color. I just got it and it’s my first tank. What do I need to do

    • Scott @ Algone
      Scott @ Algone says:

      That green water is free floating algae. Algae requires water, light and nutrients to grow. You should limit the lighting of your tank to just a few hours when you are able to enjoy the aquarium. Most Fish don’t live in brightly lit environments so they really don’t require tons of light over prolonged periods.

      How to control algae & clear green water
      What is green aquarium water? What causes it?

      Also be sure not to overfeed. Overfeeding is the number one source of waste entering the aquarium. That waste ends up as nitrate, which is the ideal fertilizer for algae. Feed no more then once daily… sparingly at that. It’s ok to feed once every other day if the aquarium is experiencing a severe algae bloom or persistent green water. Fish have a slow metabolism and don’t require anywhere near the amount of food often recommended.

      Overfeeding Aquarium Fish

      Lastly, avoid any large water changes. It can be tempting to make big changes when battling green water, but often times this only makes things worse because it further disturbs the balance of the aquarium. Always make small incremental changes. Some patience is required when maintaining a fish tank.

  3. Maureen says:

    I have a new 28 gal. tank used a biosoil gravel for plants then covered it with gravel, both according to directions. Today was the first time I cleaned my tank using a Python vacuum. It sucked up both the gravel and biosoil. I tried changing the suction and it still didn’t work as in the video. I probably changed half the water, which is a no no. Also my fish were very scared. The water cleared quickly with my good filter but that may not be enough. Any suggestions?

    • Scott @ Algone
      Scott @ Algone says:

      Hi Maureen, you really just have to avoid poking the gravel with the siphon. Just move it close to the substrate surface to suck up any waste accumulating there. As soon as you are picking up substrate, move the siphon further away from its surface.

  4. Deepak says:

    Hi j am an aquarium lover. I have Jewel 180 vision aquarium with 20 fishes in different categories like Oscar, parrot ,Silver shark, shark fish, green terror ,Malavi and all. I am using external canister JBL e1501•Need your expert advise

  5. Newswordtailmom says:

    Looking for help! I all of a sudden have 22 baby swordtail fish! And only two adults. That is all that is in the tank. I have a heater, but wondering if removing it will keep them from breeding more. How can I stop the breeding??

    • Scott @ Algone
      Scott @ Algone says:

      You can try to change the temperature in an effort to stop breeding, however we don’t advocate for making environmental conditions less favorable for fish for any reason at all. Unfortunately, swordtail fish are live bearers that breed easily. Your best bet is to keep just one swordtail and add another species of fish, avoiding pairs of other live bearers such as guppies of course.

  6. Toni Badr says:

    I have a 55 gallon tank , slowly my fish started to die from what as fish pet store thought might of been Popeye and suggested I use a medicine for them , well lord did it turn my beautiful tank so green I couldn’t see anything in it !! Now I’m struggling to get it clear 😢 I can see my fish again and starting to see plants and decorations in it , but its a very slow and painful process… Can you please help me 😲

    • Thilo
      Thilo says:

      Popeye is more of a condition or symptom rather than a disease itself. There are multiple causes and remedies, but the pet store likely gave you a broad spectrum antibiotic. The antibiotic then does not differ between good and bad bacteria and will go after the beneficial bacteria as well. With the diminished bacteria colonies the process to reduce and process waste is limited. Add some dead fish and you have an abundance of waste (dissolved organics, nitrogen compounds esp nitrates, and phosphates).
      And with that, you have the perfect ingredients to start the water to turn green.

      The solution is simple but will require some time: avoid large or frequent water changes, reduce the feeding to once every other day to whatever the fish can eat within one minute. Increase oxygen levels, remove nitrates and dissolved organics (Algone). Be patient, it will take a few weeks to clear. If you use fertilizers, discontinue those. If you use water conditioners containing bacteria, discontinue those. If you use pH regulators, discontinue those as well.

  7. Dee says:

    Good information I’m just started to keep fish I have a 50l tank I have a pair of bettas and a swordtail what other fish do yous recommend to put in. I plan to get a few nano tanks to get single male bettas any info would be gladly received thanks.

  8. John says:

    Some advice please. I am new to keeping fish and have had a small aquarium for appx 6 months, up until now everything has been fine, however, I am now finding that I am having a problem with mould growing on some of the ornaments and plants I have installed. Could you possibly give me the cause of this and how to resolve it please? Thanks in anticipation.

    • Thilo
      Thilo says:

      The cause is likely overfeeding and a lack in maintenance. You can remove and prevent mold by not overfeeding and regular maintenance which should include vacuuming the gravel. On plants, make sure the substrate and lights are appropriate for the plants to grow properly. If the plants do not have the environment to grow, they will decay and cause all kinds of issues.

    • Donna Fischer says:

      I am having a problem with my aquarium I have a 10 gallon one I keep seeing a brown buildup on the on the glass plants and decorations What can I do to resolve this. I have 4 small goldfish.

      • Scott @ Algone
        Scott @ Algone says:

        Sounds like algae growth. Check your nitrate, as algae feeds off this nutrient. Even if your nitrate reads low, the best way to minimize it is to avoid overfeeding. Feed no more then once a day, sparingly. While trying to clear the algae up, feed only once every other day, also sparingly. Fish have a slow metabolism and this won’t have any ill effect on them. You should also do regular water changes, but be sure not to exceed 15% of water every 3 days at most. Changing too much water, while well-intentioned, only leads to ore problems as it throws the tank out of balance. Lastly, check out Algone for nitrate reduction and water clarification. Algone is an excellent product that promotes aquarium health.

  9. Somber says:

    I recently revived a .25 Betta fish tank, and am wondering about how I should maintain it. I’m not sure whether I would need a filter for such a tiny tank.

    • Scott @ Algone
      Scott @ Algone says:

      I would encourage you to get a bigger tank. 1/4 gallon is simply not big enough to to be considered a healthy and humane size for any fish. Consider a 5 gallon tank. And yes, filtration for said 5 gallon tank is highly recommended since it filters out pollutants and helps maintain a healthy and balanced environment for aquatic life.

  10. Laurel says:

    We have a newly established tank and we are using well water. Our water is cloudy and our ph and ammonia levels are very high. We have used ph down, actually more than recommend, but that hasnt worked, and the ammonia is still very high. Any ideas?

    • Scott @ Algone
      Scott @ Algone says:

      Two options to consider are investing in a good reverse osmosis filter or using bottled spring/distilled water.

      A quality R/O unit will remove many pollutants which cause a rise of pH in the water. It should also remove ammonia.

      Also be sure to use a quality water conditioner to remove chlorine and heavy metals from your water. Though most well water is not treated with chlorine, this could be your source of detectable ammonia. Unfortunately, water conditioners will have no effect on the pH.

    • Scott @ Algone
      Scott @ Algone says:

      Yes, you can use tap water. But you should use a water conditioner to neutralize any chlorine and remove heavy metals before adding it to the fish tank. Also make sure the water is at about the same temperature you maintain the aquarium at. Lastly, checking your tap water for nitrate and proper pH is also a good idea. Your local pet store should have a variety of conditioners and test kits available for you to choose from.

    • Scott @ Algone
      Scott @ Algone says:

      Ideally you should add the conditioner to water before you add it to the tank. Use a bucket or other container, add water and conditioner to remove chlorine and heavy metals, then add it to the aquarium. Do this ever time you change water.

    • Scott @ Algone
      Scott @ Algone says:

      Probably not the best idea. Changing water too frequently, or changing too much water at once can throw off the biological balance of your fish tank.

  11. Ernest London says:

    Thanks for the aquarium maintenance tips. My wife and I are going to buy an aquarium soon, and I want to make sure I know how to take care of it and the fish. I appreciate that you mentioned to vacuum the gravel every other week. I didn’t know it needed to be done that often, but I will be sure to schedule it.

  12. Elizabeth says:

    Hi! Thanks so much for providing this resource. Regularly–including just in the past couple of months–I’ll notice large aquariums in restaurants that do not appear as though they are being maintained properly. The most recent one I am concerned about not because of the appearance of the water (It looks clear.) but the amount of it. We’ve visited this restaurant maybe 5 times in the last month; it opened in April. During that time, I’ve noticed that the water seems to decrease in volume. Last night, it appeared to fill only 2/3 of the tank. There are easily a dozen large fish (each the length of an adult’s hand) in there, and the guys running the restaurant seem to be young and inexperienced. From your article, I do understand that water needs to be removed in increments every two weeks; I take it that means you replace with “fresh” water what you remove? Knowing virtually nothing about fish care, I feel awkward approaching the owners, but . . . I sincerely doubt animal control will do anything about this. What do you recommend? And is there a rule of thumb for the volume of water needed, based on the number of fish? Thank you.

    • Scott @ Algone
      Scott @ Algone says:

      Generally we recommend about 1 inch of fish per 2 gallons of water for a healthy aquarium. As for the water changes, that is correct, you replace the water you extracted with fresh water. Most tap waters need treated with a conditioner before it’s suitable for fish. The conditioner removes chlorine and heavy metals which can be harmful for aquatic life.

  13. John says:

    According to the article, the water in an aquarium ought to be changed every two weeks. This is good to know since my wife would really like to have a custom aquarium installed in the entry way of our home. I feel like having an aquarium is a big responsibility, so we’ll be sure to have the water changed periodically with any and every other necessary step needed to keep our fish healthy and happy.

  14. Carlos says:

    I have a 55gal tank been in operation over a year there. Do keep up with water changes and maintenance…there is a build up in the plastic palnts and decore. Should I clean these???

    • Thilo
      Thilo says:

      Yes you can remove the plastic plants/ decor and give it a good scrub. Best done with regular water, bleach or soap if needed. To be safe, rinse the plants/ decor in conditioned water (water with conditioner) before adding them back in the aquarium.

  15. Bill Doke says:

    How do you get rid of fungus in a fresh water tank? There is a white fuzzy growth on the sails of a ship in our aquarium. We’ve already lost almost all of our fish from this in the past. We have some beautiful angel fish that we would hate to lose.

    • Thilo
      Thilo says:

      Mold or fungus can be observed on silicone (suction cups/ tubing) or wood (drift wood). These are nutrient providers allowing the mold/ fungus to grow. Ornaments come pre-treated, but it is always advisable to soak any items in water to make sure they are safe to use.
      Now, fungus or mold are not really a threat to fish. While it is unsightly, the cause of your fish dying is likely unrelated to the issue. Please check your vitals (ammonia/ nitrite/ nitrate/ pH) and increase water flow and oxygenation by adjusting your filter outlets (stronger current on the water surface).

  16. Rahul says:

    1 week before i buy 8 chiclet for my aquarium. I have one oxygen filter & cleaner filter(fixed it with each other) and i started this filter 24 hours daily. Bt now 1 fish is dead & more 1 fish is not wel and its seems that this fish is no longer with his partners. I added one pinch of salt in this water. How can i do now?

  17. Sierra English says:

    I am trying to start a fresh water aquarium , with a frog , maybe a catfish , snail , crab of some sort , sharks , can you tell me if these species are compatible ? if not , which wouldnt do well ? also , what type of filtration system would fresh water take?

    • Scott @ Algone
      Scott @ Algone says:

      The shark may be an issue. It’s best to visit a knowledgeable aquarium store and have them advise you on compatible fish they sell. What you are trying to do is start what’s called a community tank (an aquarium with various fish species). There are many fish that are suitable for this. You’re basically looking for non-aggressive fish that aren’t territorial.

    • Wil says:

      I have found that all my sharks, bettas or angelfish really need is space. If they have an area they can call their own and they dont feel threatened they are fine. Some fish seek trouble though like tiger barbes and oscars. However your shark wont mess with any catfish or frogs however i have never kept snals or crabs in my aquariums. Just ghost shrimp which are pretty cool but really sensitive.

  18. Don says:

    This summer we brought home fish from the fair and we’ve done this every year and never had a problem, but this time most of our fish died. We cleaned up the tank but one of our fish got the worse case of dropsy but it was to late to correct it so most of our fish died from that. Today I cleaned out the tank top to bottom and the fish who had dropsy is better now I believe. After cleaning it deeply, is it safe to buy more fish or is the fish always contaminated? It’s a 30 gallon tank and he’s a big boy so I don’t want to get rid of him or get another tank. Just wanna know if it’s sage to buy fish again. Thiughts?

    • Thilo @ Algone
      Thilo @ Algone says:

      Dropsy is a symptom associated with a bacterial infection. The fish should be quarantined and treated with an antibiotic. Make sure the quarantine tank is well aerated and add a pinch of salt to the water (one time application) to ease wit the breathing. Dropsy is not contagious so If the other fish do not show any signs, you can introduce new fish to the main tank.

  19. Jaiveer says:

    Hello any body else there to answer me, i am very much interested in buying algone for my tank it needs to reduce nitrate level . Is algone available in INDIA if yes where to get it and how much it costs in rupees instead of dollars. Is algone suitable for Indian whether condition. How to get algone in INDIA, how to algone, is it suitable to b use in India, how it works ? I am interested in buying this product. And also these types of products are not easily available in India . I’ve seen the review of this product I quite supriced of it because all the customers were fulfilled by the product? For details can I call you? Please give all the details on algone please don’t regret to answer. Thank you.

  20. Jaiveer says:

    Thank you for the answer, I’ve another question on the blood parrot is black spots are eligible to kill a parrot or it cannot.what should I do for the remedy for the black spot is the blood parrot can easily to different environment if yes how many days it would take to adopt the environment is that important to play with the fish.

    • Thilo
      Thilo says:

      The acclimation time depends on water chemistry and quality. Stress spots are a symptom not a disease. Stress can lead to all kinds of issues if the cause is not corrected. Good husbandry will be the key.

  21. Jaiveer says:

    Help caution, As I have a new fish its a blood parrot it was too scary I’ve bought it yesterday only till now its not leaving out of the filter motor it stays only back of it and also it does not eates the food on my presence after I vacated the place where located the tank its finishes of the food. And I think so it has black spots on its body is that any disease like white spots. If so what can do for it. And also I can’t check the ammonia level nitrate level and tempreture level because I don’t have that. Please be sure of answering all my questions.

    • thilo
      thilo says:

      New fish need some time to acclimate to their new environment. The black spots are likely stress spots, which the Parrot Fish is prone to. Keep in mind that the fish traveled and was held in more than one aquarium before making it to his new home. Eating is always a good sign and if the aquarium is well established and appropriate to the requirements of the Parrot, the fish will adapt nicely. Give it a few days.

  22. Nishi says:

    I HV recently bought an aquarium approx 18*18 inches and as recommended by pershop we added 14 fishes: 3 goldfishes, 2angel fish,2 black goldfishes, 4 guppies, one redcap,one crocodile and one fighter. They started dying soon one by one as they became lazy and their Fin and tails were reducing in size and shape. We returned many fishes as we saw the symptoms. Even crocodile fish died. Now only 2 guppies r left. We r wondering what went wrong. We fed them twice a day approx 2 grains or less per fish.

    • Thilo
      Thilo says:

      If you fill a square glass container with water, it is just a square glass container with water. To make the setup habitable for fish, the glass container needs to develop bacteria to provide a safe environment for the fish. Once the container is established, it becomes an aquarium.

      Once you introduce fish, the aquarium cycle starts. Fish create ammonia, bacteria settle to break down (oxidize) ammonia into nitrite, then another batch of bacteria oxidize nitrite into nitrate. At each stage, ammonia then nitrite, will spike to fatal levels. This is likely what killed your fish. For now, do not add anything, let the two remaining fish cycle the aquarium. Once the cycle is complete, you can add more fish (one at a time). Monitor your water levels.

    • Amit says:

      As u observed ur fish’s fins scattered and reduces – It is a result of white spot disease. Results laziness in fishes and heavy breathing bcoz their gills and fins are infected. So raise ur tank water’s temp up to 86 degree Fahrenheit and then add aquarium salt. repeat it after 4 days. fish will be healthy …….

  23. Kellie says:

    Hi, we established (cycled) a 10 gallon tank had the water tested, all was good so we added a molly, two guppies and a tetra. Since then the water test levels have been like a rollercoaster. They were only stable for maybe a week after adding the fish. Last visit to the local pet store we were advised to do a water change using spring water and no chemicals were necessary just to add back in a portion of the old tank water for bacteria and putting the fish right back in was fine to do. Now the Nitrate between 40-80 and Nitrite between 3-5 levels are off. Please help

    • Scott @ Algone
      Scott @ Algone says:

      When you add new fish to an aquarium, the biological balance will need to re-adjust. The more fish you add at once the bigger the adjustment needed. Adding 4 new fish at once to a 10 gallon tank will definitely throw things out of balance. Basically the “cycle” has to adjust to handle the increased waste that is being produced by the added fish. A working aquarium is a balance between waste production (uneaten fish food, decaying plant matter, fish excrement…) and the beneficial bacteria. When you add fish (increase waste production) the nitrifying bacteria colonies require time to adjust in size in order to handle the break down of that waste. I would cut down feeding to once every other day for the time being and stick to incremental water changes of about 15% every 4 – 5 days until there are no signs of ammonia or nitrites left. Nitrates have to be managed on an ongoing basis by controlling waste production (don’t overstock with fish and never overfeed), performing regular water changes, maintaining the filter and siphoning the gravel for waste particles, and the use of a nitrate reduce such as Algone.

      Bottom line is you always should make small incremental changes to any aquarium. The smaller the tank volume, the more delicate the balance.

  24. Tracy Copertino says:

    Hello 🙂

    I am new to the fish keeping world. I am trying to learn as much as possible. I have a basic 10 gal tank. As I vacuum the gravel the water level decreases a lot so should I be adding water as I clean? Is it possible to use bottled water? Purified? Distilled? Or is tap better with the recommended neutralizers? I have the water conditioner only. Should I use anything else? And what about the light above the tank? When should I use the light?

    • Scott @ Algone
      Scott @ Algone says:

      You can use any of those water sources. Tap water with a water conditioner should be fine. You can check it for nitrates to be sure they are low to undetectable just to be safe. Set aside the water to be added before siphoning the gravel. Make sure it’s close to the same temperature as the tank’s water. Also avoid large water changes. Try to keep it around 15% (lower the then 20% for sure) each time you clean the gravel.

      You can run the light for a few hours when you spend time in the same room the aquarium is setup in. Provided the aquarium isn’t in complete darkness otherwise, there is no need to run 8, 10, 12 hours of light. That will only increase algae growth in the tank and fish in nature aren’t exposed to that much intense light anyway. Aquarium lighting, with the exception of plant and reef tank, is more for the benefit of the observer rather then the fish.

  25. Misheck says:

    Hi guys, how often do I have to change water in ma fish tank n hw often do I dechlorinate the water?

    Thanx in advance

    • Scott @ Algone
      Scott @ Algone says:

      You should change 15 – 20% of the water every 10 – 14 days. You should only use water conditioner to treat the water you are using for water water changes once before adding it to the tank. If you have a heavily stocked aquarium, you may need to increase the frequency of your water changes to weekly.

    • Scott @ Algone
      Scott @ Algone says:

      Always use water from the cold tap. If it is colder then room temperature, you can leave it sit in a bucket overnight so it doesn’t lower the tank temperature too drastically. Also be sure to use a water conditioner to remove chlorine and possible heavy metals.

  26. ren says:

    hello, i have a 24 x 12 x 12 aquarium with 1 submerged pump and filter and three kois/carp at the moment, i feed them every morning only and evenly distribute the food. the local vendor said to stock up on tap water 1 or 2 days before using it to change the water in the tank, is this advisable? also i bought a chlorine neutralizer, is this okay to use on the tap water before i put it in the tank? and does koi/carp need a janitor fish?

    • Scott @ Algone
      Scott @ Algone says:

      You can set aside tap water prior to doing water changes. The only reason for doing this would be to let any chlorine/chloramine dissipate naturally. Since you are using a conditioner however, you should be ok to use the water following treatment as per the manufacturers usage instructions. The added benefit of a water conditioner is that most will also remove heavy metals from the water.
      A janitor/cleaner fish can usually be safely added to a koi tank if desired.

  27. Abheek kumar says:

    Hi scott,i own a medium size aquarium. When i replaced the whole aquarium water to new water.i observed that the water was still in white colour and most of my aquarium fish died after replacing the water.why this is happening ,please answer me.

    • Scott @ Algone
      Scott @ Algone says:

      Hello, it’s never a good idea to change all the water at once. Basically you will be starting from fresh and will need to re-establish the required biological filtration and nitrifying bacteria. See this article for more information about the Aquarium’s Biological Filter

      When you replace all of the aquarium water, you lose nitrifying bacteria responsible for breaking down the waste in your aquarium. Due to this ammonia is likely to spike and have negative consequences on your fish. Ammonia inflames the fish’s gills and makes it difficult for them to breath. Unfortunately prolonged exposure to ammonia will lead to fish death.

      Here’s some more recommended reading so you can gain a better understanding about the biological and chemical makeup of a healthy aquarium:

      The Nitrogen Cycle
      Nitrifying Bacteria
      What causes milky white cloudy aquarium water?

  28. Nicholas says:

    Hi I’m new to fish keeping so I asked the people at my local Petsmart what combination of fish I could safely get for a twenty gallon aquarium and they told me 4 Sunburst Wag Plats 3 Cory catfish 3 Mollies 2 Bloodfin Tetras and that I could get a female Betta is that all right

    • Scott @ Algone
      Scott @ Algone says:

      The Platys, Corys, Mollies and Tetras are all quite common community fish. Just be careful with the Betta. Female Bettas are generally not a problem as they aren’t as aggressive as males but they will likely chase other fish away (from their established territory). For that reason be sure to provide adequate room and also various hiding places for all of your species to establish their territory within the tank. Also remember not to overstock the aquarium. You do not mention the size of the tank but here’s a quick overview and some guidelines to properly stock the aquarium.

  29. Doug Languell says:

    we have got 4 glo fish in a 5 gallon tank with a pleco to eat algae. my question is :
    Is it a good idea to move the fake plants around in the tank after cleaning them and the gravel.

    • Scott @ Algone
      Scott @ Algone says:

      Not sure what the purpose is for moving the plants around but yes, it’s ok to move them if you wish. There’s no real maintenance benefit from this but if you want change the aquascape you can. Keep in mind though that this is the home to your fish and they usually establish territories within the fish tank. Changing things will disturb this so it’s best not to do it all too frequently.

  30. Priyanshu debnath says:

    Hello..have read the above problems and their solutions. ..its really helpful..
    I have 4 gourami’s, one crocodile fish and recently bought 2 small goldfish…i have this aquarium for nearly more than 2 yrs…but previously my fishes had i had bought a new bigger aqurium 1 yr ago…my fishes almost all the time stay floating on the surface of water…plz suggest me something and previously my fishes would grow very big and it uses to be healthier fishes. .but after i have bought the bigger aquarium my fishes doesn’t grow like previously it used to be and my gold fishes are also not so much healthy…plz help me…plz suggest something. .☺☺☺

    • Thilo @ Algone
      Thilo @ Algone says:


      I think you should take a look at your water parameters. Especially ammonia/ nitrate, pH and carbonate hardness (kH). If the parameters are not within the specifications fish will be effected adversely. More tolerant but not quite ideal parameters cause stress, which can lead to stunned growth. It also weakens the immune system making fish vulnerable toward diseases.

  31. Aatray Maheshwari says:

    Hi Scott,
    I have recently bought an aquarium having 2 angelfish, 2 red caps, 1 silver shark. One of the two angelfish frequently attack other fishes and bite their tails. What should I do to prevent it?

    • Scott @ Algone
      Scott @ Algone says:

      There isn’t much you can do about it. Best practice is to research fish compatibility before buying any. If a situation arises you should assure that you provide plenty of hiding spaces for different species of fish. Also, if possible you can try feeding several small portions a day. Be sure to spread the food and not to spot feed. Take care not to overfeed however, as this will only lead to water quality issues later on. As a last resort, you should consider the size of the aquarium and determine if it is large enough to provide enough space for all your fish. I hope this helps. I know how frustrating it is to watch a helpless fish constantly constantly get nipped by others.

  32. Asif says:

    Hello Scott,
    Can you please suggest how many times I should feed them in a day. And can I give them natural foods like bits of leaves or cooked rice or something else. I would like to know what natural food I can give them.

    • Scott @ Algone
      Scott @ Algone says:

      We recommend feeding fish only once daily and sparingly at that. Fish are natural grazers but we tend to feed them to benefit our schedule and because we want to interact with our fish. Overfeeding inevitably results in increased water pollution which will degrade the quality of the aquarium and the health of the fish.

      You can certainly feed lettuce or other leafy vegetables to your fish. Vegetable clips are widely available at pet stores and can be used to conveniently place lettuce, etc inside the tank by attaching it to the glass via a suction cup. I don’t think rice is a good choice however. It’s purely a carbohydrate and lacks vital nutrition fish require.

      The healthiest food choices are live foods. A quick google search should return a lot of results regarding live fish foods. It would be far too much for me to get into here in the comments, but google should put you on the right track.

  33. Jenn says:

    I have a 75 g gall under both glass hoods is covered with algae , best way to clean it and keep it from coming back . Also in corners, any tricks for this ? My help has left me?

    • Scott @ Algone
      Scott @ Algone says:

      Hi Jenn, the best way to clean hoods is to take them off and scrub them in the sink. Careful if you use any soap, if you do, make sure you rinse the lids thoroughly because you don’t want any detergents in the tank as they will kill beneficial bacteria. It’s best just to use water and a scrub pad to clean them. Keeping the algae from coming back can be as simple as reducing water splashes at the tank’s surface. This is what causes the lid to become wet and eventually algae to take hold. Surface splash can be reduced by either assuring that you keep the water topped off or by lowering the filter’s return so it is stays submerged in the water.
      For the corners I would recommend this.

  34. Owais Rashid says:

    My name is Owais and I’m new to fishkeeping. I have bought a medium sized aquarium (18″ * 12″ * 12″). The local vendor gave me 5 fishes. I don’t know what breed they are. Two of them are orange, one is orange and white, another is silver and a black one. I have a filter, air pump and a heater. It’s the first day for the fish in the aquarium but I noticed that they are confined mostly around the heater. The black one just lying just below the heater. Other 4 also don’t roam much. I have not fed them today as suggested by the vendor. Also they are mostly near the gravel and don’t come to the middle or the top portion.

    Can you please suggest.

    • Scott @ Algone
      Scott @ Algone says:

      Hello, some fish will prefer the top, middle or bottom of the aquarium. This varies depending on the species. Also, there are many fish that prefer to hide within the tanks ornaments and decorations. Again, this depends of the specific species. You could take pictures of your fish and visit your local aquarium store. They should be able to help identify the species you have and can also recommend other compatible fish that will compliment your fish tank.
      Also be sure to give the fish some time to acclimate to their new surroundings and you may very well find that they become less shy with time. Especially when they begin to associate your movement near the aquarium with feeding.

  35. Amie says:

    Hi, I’ve a 20g aquarium with tropical small fishes, I have them for just about 2mos. I just noticed recently that some of the fishes have shiny spots like a grain of salt in them and one has ragged tail fin. Are these signs of diseases? What should I do or what does my
    aquarium need?

  36. Saurav says:

    I have 2 angel fishes, 2 gold and 2 white fishes…. I bought them yesterday. My tank capacity is 1*1*1.5 i have 6 medium sized and 3 small fishes. I added water to the aquarium (tap water) and then added fishes after 2 hours. Till now no deaths but i feel i see a little redness in the gold and white fishes after i turn on my filter. Also the angel fish looks too shy and lazy… It takes less or no food or very late. It also seldom visits upper part of water. It looks ok but i feel a hunch something is wrong. Please help.

    • Scott @ Algone
      Scott @ Algone says:

      It sounds too soon to diagnose any problems in your fish tank. Redness may be an inflammation of the gills due to ammonia and nitrite which will be present at some point during the first few weeks of a new aquarium. Once the aquarium has cycled, ammonia and nitrite should always be undetectable and therefore shouldn’t present a problem for your fish.

      Further, Angelfish are well known to be docile and will seek out hiding spots in the aquarium. They are not an overly active species. You should always provide ample plants (real or artificial) for them to hide in.

      Here are some links with valuable information concerning the setup of a new aquarium:

      The Aquarium Nitrogen Cycle
      New Tank Syndrome
      Feeding Aquarium Fish
      Aquarium Fish Stress

  37. Rohan says:

    Hi Scott – i have bought an aquarium 2 days back. its a 250Lt., 1.2Mt long aquarium with 16 fishes including catfishes, eel, goldfish, suckers etc. the first night i fed them at 11PM. next day, the fishes count at around 4 PM had become 15 and one catfish had a bulging stomach with a goldfish tail sticking out. my guess is it was eaten by the catfish. how can i prevent future cases like this? what is the ideal feed to fishes per day? twice? thanks.

    • Scott @ Algone
      Scott @ Algone says:

      Hello Rohan, I don’t know if there’s a foolproof formula to avoid larger fish going after smaller ones. While feeding may help, it is best to stick to non-egressive species (herbivores). You may also want to keep to fish that do not vary greatly in size.
      Our feeding guideline is usually only once per day and sparingly at that. The problem with feeding fish is over-feeding fish. Since an aquarium is a closed-loop ecosystem, great care needs to be taken not to pollute the aquatic environment. While a generous feeding schedule of ample food may prevent what you’ve experienced, the resulting waste accumulating will cause the water quality to quickly deteriorate. Harsh water conditions, cloudy green water and excessive algae growth are conditions caused by accumulating waste.

      Try feeding twice a day, morning and evenings, but only a pinch. Please do not use the guidelines provided by most fish foods that state to feed an amount the fish can eat in 3 – 5 minutes. That is far too much food and will spell doom for water conditions in the long run.
      Also provide good cover and hiding places for your more timid fish.

  38. Jim says:

    I just got two of my first ever fish today and they seem very happy in their 20 gallon tank I have fake plants and a couple of structures with rocks at the bottom and the bigger one is eatin all the food, the behavior of the smaller one seems like it backs off when it comes to eating time what should I do?

    • Scott @ Algone
      Scott @ Algone says:

      This does not sound like unusual behavior. Some fish will hide when people approach the tank. It could also be attributed to territorial behavior of the other fish. This too is a normal situation in a fish tank. To make sure all fish eat in this case, avoid spot feeding. A pinch here and there at different locations of the aquarium’s surface will assure all fish have an opportunity to eat.

  39. tony saludo says:

    is it good to turn off the air pump every night and turn it on in the morning? or should I keep it running 24hrs

    • Scott @ Algone
      Scott @ Algone says:

      An air pump is generally not a required piece of equipment. Oxygen primarily enters the aquarium through surface agitation. Most filter’s returns create enough surface movement to adequately oxygenate the fish tank. So to answer your question, provided there is constant surface movement in your aquarium, there is no need for an air pump at all hence turning it on and off at set times will not have an impact on your fish.

      Check our ‘Oxygen in the Aquarium‘ article for more information.

    • Scott @ Algone
      Scott @ Algone says:

      Distilled water is generally ok to use in aquariums but why take the risk of contamination by using water from a dehumidifier? Personally I would pass on trying this.

  40. Mahesh says:

    I have a tank 5 * 2 * 2 ft size. What will be the water volume it holds in liters as well as gallons? I use ground water. There are 20 fishes which includes pirhana, parrot, sharrk, tin, cat fish, oscar, sucker-punch. I use external filter, oxygen motor & a heater. I feed them twice a day, only pellets, which they finish it within 2 min. The problem is water looks dirty very soon within 3-4 days from the time replacing of water & cleaning the filter. I found it too difficult to clean through the gravels & therefore i removed them. Replacing 20% of water doesn’t make much difference. So I have to change 90% of water every fortnight & that too becomes dirty within 4 days. Moreover, most of the fishes specially sharks gills becomes red & color goes pale. Adding medicine gives temporary result. Kindly guide me how to look after my fish.

    • Thilo @ Algone
      Thilo @ Algone says:

      The water volume would be 150 US Gallons or 566 Liter and from your description your tank is either overstocked, overfed, or still within the initial cycling period. Red inflamed gills are a sign of ammonia, which would support the notion of a disturbance within the beneficial bacteria. This can be due to a new tank, or significant changes that influenced the colony. Adding fish, medication, overfeeding can disturb the colonies.

      To start, the feeding should be reduced to whatever the fish can eat within one minute per day (rule of thumb). You can feed every other day to help reduce the waste and until the bacteria can catch up. The filtration, you can use filter material (polyester fibers) which will help to remove particles and waste at a higher. Replace the fibers often. Test your aquarium and the ground water. Make sure pH nitrates and kH are within parameters and ammonia is undetectable.

      We can’t of course summarize fish keeping in a few sentences, but please feel invited to browse our site for helpful information. You can email us directly for any assistance we can provide.

  41. Sircar says:

    Thank you. Your guidance was useful. I have got a pack of Algone. By mistake, I have got the pack for tanks of 110 gallons and above while my tank is actually about 10 gallons. I kept a pouch for a day and found the water not fully clear. Will this be a problem ? Can I continue to use this pouch ?

  42. Sircar says:

    Our goldfish have been getting white fungus which started with the tail and then spread to the rest of the body. Anti fungal drops helped temporarily but the fish eventually died ? The water had been changed completely once in 3 weeks. What could be the reason for the fungus ?

    • Scott @ Algone
      Scott @ Algone says:

      A good place to start would be here:

      Generally fish are more receptive to disease when they are stressed. Stress can be caused by imbalances in the water and poor water quality.
      While a complete water change may be done with good intentions and is likely more harmful because a big change like this will cause a lot of stress on your fish.

      Introducing new fish to the tank may also introduce bacterial or viral fish diseases. Some diseases may lay “dormant” until fish are susceptible because of increased environmental stress caused by water conditions.

      Bottom-line, it is vital to keep the aquarium balanced. Small incremental changes are recommended even when adjusting big imbalances.

  43. Kaylin says:

    My betta fish’s bowl is unhealthy and needs to be transferred to the new bowl I’ve got as soon as possible. It’s been about 2 hours now that I’ve used chlorine tablet in the new bowl to remove chlorine from water and I’m beginning to get worried about my betta’s health he needs to be transferred to the new bowl. Is it safe to transfer him to the new bowl if just chlorine treated with tablet 2 hours ago

    • Scott @ Algone
      Scott @ Algone says:

      It should state on the directions of the product how long treatment takes. Liquid products usually work instantly and I believe the tablets work quickly after they dissolve. To be safe you should consult the directions or call the manufacturer of the tablets.

  44. abhishek says:

    i had 25 fishes before a day .yesterday i changed there water and after that my twelve fishes died till now.
    pls suggest how to change water plus proprply care them also at what temperature i have to put there heater on and for how much tim i have 3 feet long aquarium .

    • Scott @ Algone
      Scott @ Algone says:

      You should always make small, incremental changes to your aquarium. Large water changes can disturb the balance of the eco system by removing too many beneficial bacteria need to break down waste in the tank. This can lead to a disruption of the nitrogen cycle, requiring the aquarium to “restart” the process. During this time ammonia spikes are to be expected. Ammonia is lethal to fish as it severely inflames their gills and makes it difficult to breath. Bottom-line is that you should stick to 10 – 15% water changes no more frequent then once-a-week.

      The heater for a tropical fish tank should be set between 76 – 80 degrees F. Please check first however what temperature is required for your specific species.

      We recommend lighting only for about 4 hours a day. Light at a time when you will be spending time in the room so you can enjoy the tank. Less lighting generally mean less chance for an algae outbreak. Provided the room in which the tank is, isn’t completely dark, your fish won’t require much bright light. Aquarium light in fresh water aquariums benefit the owner more then the fish.

      • Scott @ Algone
        Scott @ Algone says:

        Water changes should not exceed more then 20% in most cases. 10 – 15% regularly is ideal. Large water changes are generally not recommended. In some circumstances they may be effective, however sudden and large environmental changes can severely stress fish making them more vulnerable to disease.

  45. satish says:

    Dear sir
    In our aquarium there is small white color species whose stick on fish and because of that one by one fish is death.
    We also change the water but there is no results this amall species is present as it is
    So kindly suggest some antibiotics for such type of bacteria

    • Scott @ Algone
      Scott @ Algone says:

      You should talk to your local fish store professional immediately. Describe the exact symptoms and they will gladly recommend a product for treatment. We do not sell medication and can not diagnose medical problems over the internet. Please see our health guide for a helpful overview of common fish diseases.

    • Scott @ Algone
      Scott @ Algone says:

      The obvious consequence will be the rise of waste. The accumulating waste will be converted into ammonia, nitrites, and eventually nitrates. While nitrates can’t be avoided in the aquarium altogether, they are commonly removed by means of regular water changes. Neglecting to remove organic waste with a filter however will likely result in far greater nitrate levels, eventually leading to algae outbreaks and green aquarium water.
      Also see:

      The less obvious result of a “no-filter” setup is that oxygen in the tank may become severely depleted. Oxygen primarily enters the fish tank through surface agitation, which the aquarium filters return usually provides effectively.
      Also see:

  46. Fish Lover says:

    Honestly, most fish tanks are pretty depressing. Taking a fish from the wide open sea and sticking them in a little bowl is kinda cruel, so keeping it clean and safe is the least we can do for the little guys, so they have a happy life.

  47. Guy Gardener says:

    My son is really into fish, so I am going to buy some for him. I am glad I read this article first though. I didn’t know about the pH requirement.

    • Scott @ Algone
      Scott @ Algone says:

      You should try to identify any fish disease and then consult your local pet store for available treatments. Here’s a brief description of some common fish diseases that may help you identify the problem:
      Another option is to talk to your local pet store professional for help identifying the cause.

  48. Thilo @ Algone
    Thilo @ Algone says:

    High nitrates is a relative term, and depends on the species and the overall environment. Tab water, treated with a water conditioner, is a safe source, but not directly linked to nitrates. With water changes, nitrates are temporarily diluted. Keeping in mind that nitrates are the end result of decaying organic matter. Algone for example removes more than just nitrates. Proteins, fats and other substances are removed, otherwise they would eventually turn into nitrates. I would say 20ppm would be safe to introduce new fish. The lower the better of course.

  49. Michelle says:

    I am planning on having Blood parrot cichlids in my aquarium. I cleaned the tank and took some of the water for testing. They told me that nitrates were too high. I bought several products to combat this problem, but still it is unstable. I was then told by a fish expert that the regular tap water is safe. Before I get my fish, how can I get my aquarium environment safe for my cichlids?

  50. Habib. m.s says:

    Its also not advisable to always leave the lighting system on for 24Hrs. This is thought that light stimulates the growth of algae which may endanger the life of fish in my aquarium. Since this will make them active.

    • Scott @ Algone
      Scott @ Algone says:

      You are absolutely correct in that excessive lighting can cause increased algae growth in the aquarium. We generally recommend not lighting for more then 6 hours a day. Less if an algae problem already exists. Of course this is just a general guide and special consideration needs to be given to aquariums that require additional and/or specific lighting such as reef tanks and planted aquariums.

      In addition to light algae also requires nutrients, especially nitrate, for growth. Therefore the lighting schedule as well as nitrate control are the best means for controlling aquarium algae growth.

  51. Agnes Buhalski says:

    My unused Aquarium needs cleaning brfore I can again put fish in it. How do I go about this? What products can I safetly use as not to harm the fish. Thanks Agnes

    • Scott @ Algone
      Scott @ Algone says:

      Thoroughly rinse the tank with clean, warm, fresh water. If there is some grime buildup on the glass then you can use any mild detergent to clean the tank more thoroughly. A window cleaner will work as well. If you do use a detergent or window cleaner, make sure you rinse the tank assuring ALL of the soap is removed. Soap residues are harmful to fish and other livestock. It is also harmful to the natural nitrifying bacteria, which is needed to keep the aquarium healthy and balanced. Hope this helps.