How to clear cloudy aquarium water

Lion fish in blue aquarium water

What is cloudy water?

In short, it’s a bacterial bloom. However it is not the beneficial bacteria normally referred to as nitrifying bacteria. Before those get to work, another set of bacteria is needed. These “scavengers” are heterotrophic bacteria, which feed off organic waste in the fish tank.

This feeding process represents the first stage of the aquarium’s natural nitrogen cycle, at which organic waste is converted into ammonia. The nitrifying bacteria on the other hand continue the process by breaking down ammonia into nitrites, and nitrites into nitrates, completing the nitrogen cycle. Heterotrophic bacteria can double in population every 20 minutes. Its growth depends on available organic waste in the aquarium. In other words, everything that decays in the fish tanks represents a food source for these scavengers. This excessive growth turns the aquarium water cloudy.

How do I clear cloudy aquarium water?

As a first course of action the gravel should be vacuumed using an aquarium siphon. This is where most organic waste accumulates and also where the scavenger bacteria initially grow. If large decorative ornaments are in the fish tank it’s a good idea to move these from time to time in order to vacuum the gravel underneath. The goal is to remove as much accumulated waste from the gravel as possible.

Some other things that will help

  1. Reduce feeding. Most organic waste introduced into the fish tank is from fish food. Overfeeding is common and probably the main cause for cloudy water problems.
  2. Do not perform large water changes. While the intentions may be good, large water changes can severely affect the balance of the aquarium leading to a further deterioration of the water quality.
  3. Consider your fish population. A severely overstocked aquarium will result in excess waste. The general rule of thumb is not to exceed 1 inch of fish per 2 gallons of aquarium water.
  4. Be patient. Taking any or all of the above actions is a step in the right direction. However, the fish tank will need time to balance and recover once favorable conditions are created.

Also see our ‘Aquarium Maintenance and Fish Care Tips‘.

And make sure you check out Algone for clearing cloudy water and removing nitrates and impurities from the aquarium.

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59 thoughts on “How to clear cloudy aquarium water

    • Scott @ Algone
      Scott @ Algone says:

      Yes, run the filter. It’s quite normal for the tank to initially be cloudy due to free floating particles from the gravel.

  1. Lou Howard says:

    I have a well established 36 gal, fresh water tank with 6 small fish in it. The water in the tank has been cloudy for about a month now and does not seem to get clear noi matter what I do. I change some water on a good schedule and do not overfeed. What is the problem?

    • Thilo
      Thilo says:

      After making sure that the water parameters are within tolerances check on your conditioner. The conditioner should not contain bacteria, if it claims to, replace the conditioner with a very basic version without bacteria or bacteria additives. Additives that influence pH can cause a cloudiness. Additives containing calcium can cause cloudy water as well as some phosphate removers.

  2. Stephanie says:

    I have brought a fish home feom where i work i bought a used 15 gallon tank and set it up had to add the gravel and water dechlorinator when i brought him home however this fish was in a big tank at work like a 200-300 gallon maybe the water has clouded up i might have over fed him cause he is used to 2 times a day however he has white strips across his eyes with a white ball in the middle of the stripe what can i do to help him and the water

    • Scott @ Algone
      Scott @ Algone says:

      Please see our summary of common fish diseases. We recommend asking your local fish store for possible treatment options. They should be able to help you identify any disease and choose the appropriate treatment.

      As far as your cloudy aquarium water is concerned, please review the following articles for additional information about the causes and possible fixes:

      White Cloudy Aquarium Water
      Green Aquarium Water
      Cloudy Water and Algone

      I would definitely recommend cutting back on feeding. You can feed as little as once every other day. Fish have a very slow metabolism and don’t require multiple daily feedings. If the cloudy water is caused from overfeeding, cutting feeding to once every other day should help clear it up again. Also consider using Algone, which is an excellent aquarium water clarifier and also reduces harmful nutrients in the fish tank.

  3. Carl says:

    Hi I have had a cloudy water issue in my aquarium now for about two weeks now I have tried fluval quick clear but it hasn’t worked.i do regular water changes but nothing,it’s not bacterial bloom

    • Thilo
      Thilo says:

      If it is not a bacteria bloom, then is is an algae bloom? You can search our site for relevant articles that will provide more detailed info. In a nutshell, algae need nutrients, water, and light. If all is available in excess, an algae bloom can occur. The best way to resolve the issue is to remove the excess nutrients (nitrates/ dissolved organics) It will take some time and you should refrain from the temptation for large water changes or any other dramatic change. It will just cause other issues, but the problem will remain.

  4. Ailene says:

    Hi, i just got a fish tank for the first time ever. I just start it 2 days ago with the filter but just yesterday i put the thermometer, light, oxygen, Conditioner and some decorations. This morning the water looks really dirty or cloudy how some people call it. What should i do? Change the water? Leave it? When can i pit fish in there? Thank you for your help!

    • Scott @ Algone
      Scott @ Algone says:

      Just let it settle for a few days and it should clear up. If you also experience a white cloudiness, that is usually a bacterial bloom and should clear up on its own as well.

  5. nydia says:

    Hi, I have a new aquarium I think is 15 to 20g, I prepared it and put some decor and filter 4 days before adding fish, I put 7 fish, the 2nd day it got cloudy, after reading here I realized this is normal. Is now clearing up, my question is about oxigen, I keep reading about oxigen levels, how can I know my fish oxygen levels are good? Oh and how often do I wash the tank? Do I remove the fish and change water? Sorry this is new to me

    • Thilo
      Thilo says:

      For as long as your filter outlet provides a disturbance at the water surface, you will be fine on oxygen. You never wash the tank, ever. Use a siphon and take 10-15% of the water out of the aquarium gently grazing the substrate. Refill the aquarium with water (use a conditioner prior to adding the water). Go this every other week. Once a month, rinse out the filter, never scrub, just rinse. We have a maintenance schedule online

  6. Steve N says:

    I have a 20 gallon aquarium, it has been home to guppies for 10 years. We got an green algae bloom that obviously, got some attention, it was right as I got the bloom under control the filter failed beyond repair, 12 hours until I could get the new Marineland filter and installed. Five hours later we lost power for 16 hours. That was five days ago. After the filter ran for 24 hours I swapped, a bit more than a third of, the water, and changed the filter packs. I still have a cloudy, milky white not green at all, water condition. The lights have been off for 36 hours. I am only seeing a 5% improvement at best. I have not experienced anything like this before, any thoughts?

    • Steve N says:

      I forgot to add, I put an extra air stone in, in case it is a bacteria bloom from the new filter getting it’s levels up. The water change I did included vacuuming the substrate. Thanks again for any thoughts you may have…

    • Scott @ Algone
      Scott @ Algone says:

      It’s probably best to just stick to 15 – 20% water changes. It sounds like your biological filtration is out of whack after all that and needs time to recover. For nitrifying bacteria to come back into a healthy balance, consistent tank conditions are required. The treatment of the algae bloom, the failed filter, as well as the complete replacement of the filter along with a 33% plus water change have likely thrown the tank out of balance. Now that everything is up and running again and no major changes are being made, time should clear up the white cloudiness. You may also wish to cut feeding to once every other day while the tank is cloudy. This will help cut down organic waste entering the tank and should hasten the process of balancing. Your fish will do just fine on that amount of food as they have a very slow digestive metabolism and really don’t require all that much food. Overfeeding is generally the number one reason for algae outbreaks and other problems related to poor water conditions.

      • Steve N says:

        That was my working assumption as well. Like a perfect storm, the aquarium balance was hit from every side at once. The water change was only to clean the substrate, after the algae bloom and crashed filter, the substrate was not pretty, haha. I think the original algae bloom was caused by a broken window treatment at the right time of the year, for there to be an exposure of direct sunlight, in the morning hours, working graves, I tend not to see early morning events, haha. For now, we wait…

  7. jennifer buchanan says:

    I have had a tank running for over a month i added my fish as i have had consistent levels. But now my water is constantly cloudy. I am fairly new to fish and got alot of info from the store i have a 15g tank i have 3 rainbow fish and 6 dwraf sharks and 3 apple snails…..could the snails be the problem??? I have plants in there as well but the snails are eating them at night.

    • Thilo
      Thilo says:

      As things get crowded, and you are pushing the limits of your tank, the environment deteriorates, especially if you have a maintenance schedule that needs improvement. Plants that are not thriving will also contribute to the issues. I take from your first sentence that you just added fish? In this case the tank needs to re-adjust to the new bioload. That often triggers a whitish discoloration sometimes followed by a greenish tint. The whitish discoloration is a bacteria bloom, the consequence of the aquarium adjusting. With all the new waste to be processed, waste accumulates until there is a sufficient amount of bacteria present. Make sure the water is well oxygenated as bacteria use up good amounts of oxygen.

  8. Jody says:

    I have a 30 gallon tank, the water is so cloudy and a touch of greenish color, I’ve added chemicals and changed half of the water. But no matter what I do it still gets cloudy, I’m wondering, could it be the well water? I hate to spend money to purchase 30 gallon of water and to have the same problem.

    • Thilo
      Thilo says:

      Yes, it could be the well water. This water source can contain contaminates that fuel algae growth, iron, copper, phosphates, just to name a few. You can have your well water tested to make sure. The beneficial aquarium bacteria, fish, plants etc have a much lower tolerance of what we would consider harmless for human consumption. You can look into a water purifying system or an R/O unit.

  9. T Anderson says:

    I have a 40 gallon breeder tank and my water is cloudy. I have no fish in the tank, I do have decorations, and substrate. I did thoroughly clean the substrate for about 20 minutes per bag. I have the Quietflow 50 filter and Aqueon 100watt heater. My ammonia levels are at a constant 0 also my nitrite and nitrate levels are 0. Am I doing sonething wrong with my tank to cause the cloudiness.

  10. mike chocha says:

    Hello i used to have like 5 or 6 tanks all over that house when that kids were in they tens that was like ten years ago, a week ago my grand daughter which she is a year and half went to the hospital she had a high fever but thank god it was just a cold any how when i arrive at the Hospital she was really upset so i took her to the lobby and we found a beautiful fish tank in a corner she initially didn’t like it until i stared to show her that fish and she calm down and ot was like she wasn’t sick at all, anyhow two later a older client of mine ask me to clean out he’s back garage it took me three hole days any how there was 75 gallon fish tank full with drifwood and i took it home wash it with a clean rag and white vinegar and then rinse with a lot of water and the driftwood i clean with a brush and lots of water anyway bought a filter for 75 gl and a light fixture for the hood in home depot set everything up and i fill the tank with water to say the least my grand daughter loves it well at least the first two days today my daughter came in and say moso soup, this thing is almost black water forget the tea or whatever also they call it , i took out all that driftwood we can only see what was in front of glass , im really disappoint it specially for my grand daughter.. I guess my question is what can i do. Ps sorry for that long as letter thank

    • Scott @ Algone
      Scott @ Algone says:

      Sounds like the driftwood leached into the water. Removing it was a good first step. Try using activated carbon in your filter, replacing it every few days until the tank has cleared up. Also consider doing a 15 – 20% water changes every 3 to 5 days as this will help clear up the aquarium as well.

  11. DJ says:

    I just set up my 50gal tank it’s been running for about two days I haven’t added fish yet because my water got milky cloudy why is this and how do I fix this

  12. Dana Hall says:

    I have a small 3.5 gallon fish tank with a small filtration system in my classroom with one goldfish in it. There are small rocks at the bottom of the aquarium. I have noticed that over the last couple of weeks (we have had the fish for almost a month now) the water has turned cloudy. I need to know what we can do to make the water sparkling again and to make sure “Fred” is well taken care of. Please advise on what I need to do to make the aquarium shine again and how do I go about cleaning the aquarium. Do I remove the fish from the tank and wash out with distilled water? I need advice. The last thing I want is to come in and have to tell my kids that Fred is dead!

    • Thilo
      Thilo says:

      An initial cloudiness (whitish) can be expected with a new setup. Bacteria settle to make the water safe for the fish. In cases, the bacteria colonies grow at speeds that turn the water withish. You can use Algone to speed up the process for the water to clear. From there, and in general, the most important factor is not to overfeed the fish. Just a small pinch per day will do. This together with weekly 10-20% water changes using a siphon to vacuum the gravel. A small aquarium is more affected by changes than a large aquarium. Temperature for one, but also chemical/ biological factors are more easily influenced due to the smaller water body. Following a strict maintenance routine is therefore of the essence to keep the water clear and the fish healthy. Please do not remove the fish from the aquarium. The fish has a protective slime coat and frequent removal might damage the protective coat.

  13. Jesus says:

    Hi i have been a fishkeeper for a while with a prtty standard 55 gallon with crystal clear water, my brother just recently got a starter kit with the ten gallon and all that, he asked me to do the set up so I cycled it washed the decorations toroughly i used water de chloeinerez and i acmimated the fish it was all good the first day but over night it got all milky and cloudy, i have never seen this in my fifty fice, what do i do?

    • Scott @ Algone
      Scott @ Algone says:

      White cloudiness is caused by a bacterial bloom. In short, the tank has to come into balance. With a new tank this usually clears up on its own fairly quick. I would recommend avoiding large water changes or any other big changes while the tank is cycling. During the break-in period, the aquarium will eventually balance as long as it is given adequate time and also conditions are consistent. Obviously your brother should avoid overfeeding and overstocking the tank as well. A ten gallon tank is more difficult to keep then your 55 gallon. The small tank volume will require more diligence because waste will have a greater impact. So again, I can’t stress enough to make small incremental changes only. Cloudy water often prompts newcomers to do large water changes with good intentions. What really happens however is that balancing the aquarium is delayed because of it.

  14. robert says:

    i have a small fish tank with 5 shubukin babies and 2 gold fish babies and 2 little fresh water fish…
    i use tap water for my fish using water conditioner.. i don’t have an oxygen pump.. my water are cloudy every time..
    and i don’t want to buy air pump…
    so what can i do……….
    and i am a starter …..

    • Scott @ Algone
      Scott @ Algone says:

      You don’t need an air pump and adding one won’t solve your cloudy aquarium water problem. It’s not unusual for a new tank to get cloudy water. In fact it’s a condition often referred to as ‘New Tank Syndrome‘. Generally cloudy water indicates increasing pollution inside the aquarium. This is best managed by feeding the fish sparingly. We recommend feeding just once a day and sparingly at that. Do not follow intersections on fish food packaging stating to feed 3 times a day however much the fish can eat in 2 – 5 minutes. This amount of food will wreak havoc on the fish tank.Feed sensibly as recommended above and also perform routine water changes every 2 weeks of about 15% of the water. Use a siphon to remove (vacuum) the gravel when extracting water for your water changes. If the cloudy water persists try using Algone. Algone is an excellent non-toxic water clarifier and helps clear up just about any type of cloudy aquarium water.

      Also see the following articles:
      Overfeeding Aquarium Fish
      Water Changes
      Clearing Cloudy Aquarium Water with Algone

  15. Nik L. says:

    I have a small 5gal tank with 4 small glofish and one cory cat. Tank has been running smoothly for 4 weeks now (one week with no fish, 3 with). I had the initial bacteria bloom during the second week which cleared up on it’s own in about 2-3 days. I hadn’t had a tank in a few years but knew this was normal for a new tank.

    I left on Friday and put just a few (maybe 3) shrimp pellets in for them to nibble on over the weekend. When I came back this morning, my tank is milky cloudy again and looks like another bacterial bloom. Is this normal? I don’t remember two occurrences of it in my old tank so this second one took me aback slightly.

    Is Algone a good suggestion to remedy this or is this also somewhat normal for fairly new tanks?

    Also, if I buy the Algone, where in my small Whisper filter should it be placed?

    • Scott @ Algone
      Scott @ Algone says:

      It sounds like your tank is still in the process of balancing itself. Bacterial blooms usually aren’t a health concern for your fish so it should be safe to wait it out. If you start to notice your fish gasping for air at the water surface however, you should take fast action with a 15 – 20% water change. Be sure to feed very sparingly during the bacterial bloom. Too much organic matter entering the tank will only complicate matters.
      Algone can certainly help with bacterial blooms as well. Algone gently aides in achieving biological balance in the aquarium. Algone pouches are thin and only about the size of a credit card, so placement in most filters isn’t difficult. If you don’t have enough space in your filter, Algone can also be placed directly in the water. Just make sure to secure it so it remains submerged, and also try to place it near the filters return for maximum water flow around the pouch. A veggie clip is very helpful with this.

      • Nik L. says:

        Oh awesome! I went ahead and ordered the Algone in the event I need it. Thank you SO much! I’ll try to slide it in with the filter cartridge. I appreciate your quick response!

  16. Fred Sponheimer says:

    i have a 3 month old aquarium and have taken my water for testing after the tank became cloudy! The fish store tested my water and found no problems but my tank is till cloudy! I have tried a partial water change but no help , i have also started feeding less ! How long should i wait for another course of action and what would that be?


    • Thilo @ Algone
      Thilo @ Algone says:

      Three months in, the aquarium is still finding its balance, The exact time frame depends on maintenance, fish or plant additions, and changes.

      There are three major variations of cloudiness. Green, milky white, and yellowish. Green is and algae bloom, white a bacteria bloom and the yellowish discoloration indicates soft water with a high plant density or driftwood. For the latter, activated carbon will solve the issue.

      For green or white, the causes are similar, and I am generalizing. Excess waste by the form of overstocking or overfeeding. Reduce either one. Feed every other day whatever the fish can consume in less than one minute. Refrain from large water changes. 10% weekly preferably 20% every other week will do. Vacuum part of the substrate at each water change. Discontinue fertilizers, bacteria treatments, conditioners with bacteria etc.

      Algone will remove dissolved organics which are fueling either cloudiness. This shortens the time frame for the aquarium to biologically re- balance. If you follow the above, it is just a matter of time and patience.

  17. Callie says:

    I cleaned out my goldfish tank maybe a month or so ago. Since then, it has become very cloudy and we even bought a new filter system. No such luck. Could it be from using tap water to clean the tank instead of distilled? Or from replacing everything in the tank? It’s a 10 gallon tank and I have an 8 year old fish that I’m worried about. What should I do?

    • Scott @ Algone
      Scott @ Algone says:

      If your aquarium was completely cleaned out, you are probably experiencing ‘New Tank Syndrome‘.

      Cloudy water isn’t usually a concern for fish health. You should check for ammonia and nitrite however. Both should be undetectable as they inflame the gills of fish making it difficult for them to breath. Prolonged exposure can be lethal. One visual indicator of this would be the fish gasping for air at the water surface.

      Other then that, make sure you don’t overfeed and you keep up with regular water changes, nothing too large though as that can lead imbalances. Also consider Algone for ammonia, nitrite and nitrate removal as well as clarifying the water.

  18. Jenn says:

    To answer your questions. Its kind of a milky white. Fish get a pinch of food in the morning and i crumble some tubifex worm cube in the evening for them. They eat all the food. Plus the plecostamus gets an algae tablet in the evening(which he devours). The fish have been getting this much food for as long as I had them. Had them in a 20 gallon for 2 years prior to getting the 30. Water changes are about 10%.
    tank consists of 6 neon tetras, 2 black tetras, 2 dwarf gouramis and a plecostamus. My other 30 consists of similar fish and its crystal clear. Both tanks are in the same area of my house. Within about 5 feet of each other.
    Water has been tested and everything looks fine. I tested it and also took a sample to two different fish supply stores hopeing someone could figure out the mystery. Water in cloudy tank srems to clear up after a water change, but the next day its cloudy again.

    • Scott @ Algone
      Scott @ Algone says:

      It certainly sounds like a bacteria bloom. I would consider cutting back on the amount of food. We generally recommend feeding once daily and sparingly at that. Fish have a very slow digestive metabolism and therefore don’t require much food. Additionally they are “grazers” and there’s always something available in the tank, whether it’s food settled in the gravel or small amounts of algae growing on ornaments or the glass.
      Also consider trying Algone. Algone balances the aquarium resulting in sparkling clear water. Algone can be used as a clarifier and at regular maintenance intervals, thus preventing the tank from becoming cloudy. Learn more here.
      I’m sorry I can’t offer any big new revelation but as stated above I would certainly start with adjusting the amount fed. Even when all the food is eaten, additional waste is created as fish excrement increases.

  19. Jenn says:

    Alright new tank set up almost a month ago. Water still cloudy. Its a 30 gallon. Same fish came out of a 20 gallon, just wanted more room for my plecostamus. 20 gallon was crystal clear. Fish not being over fed.. They are getting exactly what they got in the 20. Gravel has been vacumed. Same gravel came out of the 20. Plus added some extra well washed gravel. No new decorations.. Same ones from 20 gallon. Doing weekly water changes. Water seems to clear up for a day and than goes super cloudy.
    I also have another 30 (set up 3 days after first tank with all new fish, recycled gravel from an old tank and old decorations) and a 10 (nothing new and set up same day as first 30) both are crystal clear. Whats with the cloudy tank any suggestions.

    • Scott @ Algone
      Scott @ Algone says:

      Is it a whitish or green cloudiness? Also, how much water are you changing each week? Also, can you be more specific about how much you feed your fish?

      Clearly there’s an ongoing imbalance in the tank. After almost a month, the tank should be fully cycled and balanced especially since you spiked it with your existing gravel.

  20. Vanessa Vercoe says:

    I set up a 65 gallon aquarium 5 days ago and two days ago I had massive cloudy water I changed about 20% of the water and used Prime during my water change the temperature of my water is 82 degrees because I have angels I’m using a 75 gallon aquaclear filter my substrate is a combination of a base layer of eco complete 40 pounds of Echo complete and and 60 pounds of aquarium gravel. I set up the tank and let it run for about 36 hours before adding my fish and 24 hours after adding my fish the water became cloudy. I ordered some aquatic plants I’m wondering if it’s okay to plant my plants in this cloudy water. Also I also ordered air stones to add oxygen to the water. Do you recommend dose in the tank with clarify

    • Scott @ Algone
      Scott @ Algone says:

      Hello Venessa! Cloudy water in a new aquarium is very common. It’s not usually something that’s harmful to your fish. If it’s not floating particles from the substrate, which usually settle within 24 hours, it’s likely a bacterial bloom. During the breaking in phase of a new aquarium, beneficial bacteria establish in the tank and can cloud the water if they’re present in over-abundance. This should clear up fairly quick on it’s own. Resist making big water changes with good intentions. Usually this will only throw the tank further out of balance.

      Personally I would not plant my tank until after it has fully cycled (broken in) which can take around 4 weeks after initial setup.

      Check these articles for more information:

      The Nitrogen Cycle
      Biological Filtration
      New Tank Syndrome
      First Aquarium

  21. Nova says:

    Help, help, help, help, help!
    I set up a new tropical 54L tank 6 weeks ago and am still getting cloudy water! I currently have half a dozen Neon Tetras and use Tapsafe and Stability when doing a weekly 15L water change. I get my water tested every week at least from my local aquatic shop and they keep telling me the water is totally fine, but whenever I try to add a new fish (a Balloon Molly) it dies within hours. I thoroughly washed the gravel, ornaments etc. before setting the tank up and as far as I know, I’ve done everything possible but I still have this problem with my fish dying. I’m on the verge of giving up!!

    • Scott @ Algone
      Scott @ Algone says:

      Hello Nova,

      Sorry to hear you are struggling to clear your aquarium. I would discontinue using Stability. It is likely causing an over-abundance of nitrifying bacteria (the beneficial ones) which will make the water cloudy. Since your tank has been setup for 6 weeks now and your water tests are good, it’s safe to assume the tank has already successfully cycled, so there should no longer be a need for a product such as Stability.
      Just make sure to feed your fish moderately, and not to overcrowd the tank and you should be on your way to a healthy and clear aquarium.
      I hope this helps.

  22. Rosemarysammie says:

    My fish tank got cloudy overnight and I’m afraid of losing my fish. My fish tank was set up two days ago for my lyretail mollies. I have 3 and a sucker fish. It’s a 15 gallon tank and I’m using a double air pump. I used tap water but put the amount stated of aquarium salt and jungle brand start right. I have a few arrangements and gravel inside, I rinsed off everything before inserting. I also think I’ve been overfeeding them and I leave the light on 24/7. I’ve turned off the light and stopped feeding them for the day till I can fix this issue. Please help

    • Scott @ Algone
      Scott @ Algone says:

      This is a very common issue. Water often turns cloudy after first setting up an aquarium. If it’s not just free floating debris from the gravel, it usually is what is called a bacteria bloom. Beneficial bacteria need to establish in every new aquarium. This process is referred to as ‘cycling the tank’ and can take up to 4 – 6 weeks to complete. During this time, ammonia and nitrite will spike. Once those nutrients are undetectable after they have spiked, only nitrate should be measurable. Nitrate is the final nutrient left in the aquarium from the breakdown of organic waste such as fish food and fish excrement. When only nitrates are detectable, the cycling of the tank is complete.

      Bacteria imbalances during the cycling can lead to cloudy water. Generally this is no threat to fish life and it should clear up on its own. We do advise to feed sparingly throughout the cycling process. This will limit the amount of waste entering the tank and will allow for a more gentle break in of the aquarium.

      Please read more here:

      The Nitrogen Cycle
      What Causes Cloudy Aquarium Water

  23. Sarah says:

    I have a 5 gallon tank set up for my boys and have established fish in it and the water has remained crystal clear. Set up an aquarium for my girls its a 10 gallon and after 2 days the water became cloudy and has been that way for 5 days now there aren’t any fish in the new aquarium so I don’t know what could have caused the cloudiness. I did use glass gems/pebbles in the 5 gallon and aquarium rocks in the 10 gallon and I washed them thoroughly could the gravel still be causing it UK become cloudy with no fish?

    • Thilo @ Algone
      Thilo @ Algone says:

      New setups are not sterile and bacteria can grow rapidly. Bacteria can be found on anything, gravel, equipment, ornament etc. Especially heterotrophic bacteria (those do not need ammonia). These bacteria can double within 20 minutes and cause a discoloration lasting for days and weeks.
      Other causes could be commercial additives such as conditioners, bacteria starters and so on. Washing off the debris is important and can cause a discoloration of the water, but that might not be your prevalent case.

  24. Alex says:

    I have set up a 46 gallon bow front tank about 4 weeks ago. Running a fluval Aqua clear 70 with a air pump. When I first set up my tank I added quick start with stress coat as water conditioner and Api ph increaser to 8.2 as I put in African cichlids. For the first 3 weeks the tank was perfect and crystal clear. Towards the middle of the 3rd week the ammonia spiked to 4.0ppm I was able to get it down to 2.0ppm. Then the end of the 3rd week the ammonia spiked to 9.0ppm and the water turned to a very thick milkish cloudy. It got so bad I couldn’t even see the the fish or decoration. It has been a week tomorrow and it is still the same maybe just a bit litter where you can slightly see the decoration and fish littly. What can I do to clear it. I don’t want to lose any fish.

    • Thilo @ Algone
      Thilo @ Algone says:

      During the break in period of a new setup, bacteria will establish colonies. These “beneficial” bacteria break down waste and ammonia/ nitrites. This makes the water safe for the fish. The process is know as the nitrogen cycle. You can read all about it here:
      In general, the water will clear up as the aquarium establishes itself. You need to make sure to reduce food intake, which reduces the amount of waste, and to increase the oxygen flow. Oxygen is required by bacteria and increasing oxygen reduces the risk of low oxygen levels which is detrimental to the fish.
      Keep an eye on the fish behavior. High ammonia makes fish lethargic, no appetite, and inflamed gills. In case the fish are acting normal without showing any signs of ammonia poisoning, you might have used an ammonia remover that reacts with the test kit, showing ammonia where in fact none is present.

  25. Amy Watkins says:

    I started a goldfish aquarium 30 days ago, I have bn doing weekly water changes and treating with dechlorinators and start zyme. On my last water change, I also changed filter, as was quite yucky looking. The water has bn cloudy now for 6days! I’m thinking its cycling over again as I did a boo boo changing filter ?

    • Scott @ Algone
      Scott @ Algone says:

      Changing the filter may have caused the cloudy water. Obviously filter changes are a periodic necessity, but you should always try to avoid making too many changes at once as this will severely disturb the biological balance of the aquarium. Using Start Zyme can also create cloudy water conditions in the fish tank. Any type of bacterial product added to the tank can lead to white cloudy water when the bacteria become too abundant. There is a chance of de-oxygenisation from this but usually it’s not a threat and the water should clear up on its own rather quickly. Definitely discontinue the use of the enzymes though.

      The other possibility is that you have a free-floating algae bloom. If the cloudy water is green, then you likely don’t have enough beneficial bacteria established. As nitrate accumulate in the tank because of the lack of bacteria, algae spores utilize this nitrate as a food source resulting in an algae outbreak. Green aquarium water is a free-floating algae bloom.

      In any case, only incremental adjustments are recommended. Also, take care not to overfeed as this introduces new pollutants into the aquarium. While experiencing cloudy aquarium water we generally recommend feeding only once every other day (sparingly).

      Also check out Algone. It’s a great product for restoring and balancing the biological balance in the aquarium. Algone removes excess nitrate among other things. We are celebrating 20 years of Algone in 2015! It’s truly become a hobbyist favorite in that time.

  26. Saradee Delcamp says:


    • Scott @ Algone
      Scott @ Algone says:

      Sorry for the late reply to this! Hopefully your water has cleared up on its own by now. Cloudy water in a newly setup aquarium is usually caused by the following two things:

      1. There are still a lot of very fine free-floating particles from setting up the aquarium. Most of this type of cloudy water is from the substrate and should clear up in a few days tops. It’s a good idea to rinse the filters with luke warm water from time to time. A lot of the particles will get caught in the filter, and some will settle at the bottom of the tank.

      2. The cloudy aquarium water may be a bacterial bloom. This is quite common in a new tank and it should clear up on its own as well. Initially the imbalance in a new aquarium can cause good ‘nitrifying bacteria’ to reproduce at a faster then normal rate, producing a white cloudiness in the water. This should also clear up over a relatively short period of time.

      See this link for more information:

      Hope this helps!

    • severiano says:

      I am having the same issue what I would say go to petco take a sample of your water and they will point you in the right direction …..thank you for your time