How to Adjust the pH in Your Aquarium

The ideal pH level for planted aquariums is anywhere between 6 - 8.5

What are the effects of pH in the aquarium?

High Alkaline

pH changes in the aquarium, even if small, can have serious health effects on your fish. High alkaline, aka basic water, can affect your fishes’ gills. If your fish dart back and forth, check your pH, as this is a common symptom of high alkaline and may result in fish death.

High Acid

An acidic aquarium can result in the production of excess mucous by your fish. This is due to an increase of toxic elements promoted by acidic aquarium water. Other observable symptom include fish gasping, hyperplasia (thickening of skin and gills), and eye damage. As with high alkaline, fish death can occur.

How do I adjust the pH in my Aquarium?

How to increase the pH in the aquarium

A common method of raising the aquarium’s pH is by adding baking soda. 1 teaspoon of baking soda per 5 gallons is generally considered a safe amount for small incremental increases.

It’s best to remove the fish from the tank prior to raising the pH. Then simply dissolve the required amount of baking soda in some conditioned water and add it to the aquarium. Once the pH is at the desired level you can re-introduce the fish just like you would when you first brought them home from the store.

You should never make sudden and large pH changes, as this will have a severe effect on your fish. Start with 1 teaspoon per 5 gallons of water and slowly raise the pH incrementally. This will allow your fish to acclimate to the new tank conditions.

Algone simplifies aquarium maintenance

• add crushed coral 

• add dolomite chippings  

How to lower pH

Using peat moss is a common way to lower the aquarium’s pH. Simply put the peat moss into a mesh bag and add it to the filter. Peat moss will gradually lower the pH. With peat moss, it is likely however that your water will temporarily discolor. It should clear up over time and you can also use activated carbon to help it along.

Other methods of lowering the pH include:

  • Decrease aeration of the aquarium
  • Driftwood will soften the water and lower the pH
  • Increase CO2 levels (planted aquariums)
  • Adding RO water

What influences the pH in the aquarium?

  • The pH level can be different before and after water changes, especially if the pH of the aquarium water and the aquarium itself vary
  • Decreased aeration will lower the pH
  • driftwood will soften the water and therefore lower the pH
  • adding CO2 will lower the pH
  • high nitrates can cause the pH to drop
  • pollutants and waste in the water will lower the pH
  • crushed coral (substrate or ornaments) will increase the pH
  • hard water will cause higher pH levels
  • using a water purifier can lower pH levels (good with hard water)
  • soft water is generally low in pH
  • RO water has a pH of 6 or lower 
  • overstocked aquariums can be low in pH

Stability is the main factor, keep in mind that fish can adapt to a pH that is slightly off their preferred preference, it is the fluctuations that causes stress and fatalities.

The pH will vary during the day, it should always be tested in the morning or evening. Always ensure that the test kit has not expired.  

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I noticed that one of my rasboras was looking pale so I tested my water. I have a 20 gallon planted tank with a beta, 5 harlequin rasboras, 4 Cory catfish, 6 neon tetras, 2 netrile snails. I had just added the rasboras a week ago and prior to that my tank had seemed pretty stable related to nitrites, nitrates and ammonia. I hadn’t tested ph lately because everything else had been fine and I have quite a bit of drift wood in the tank. I tested the ph today and it was really high (> 8). I tested my… Read more »


It could be hard water, especially since you have a high pH in the tap water. This by itself, but in combination with less than optimal maintenance (regular water changes, cleaning of substrate etc. water will increase hardness. The substrate might contribute if it contains calcium.


The substrate I have (I can’t remember what I used) is supposed to lower the ph. I just checked the substrate in store. I do weekly water changes but I haven’t been doing more than partial substrate cleaning every week so I don’t disrupt the bio filter. If it were from poor tank maintenance, would I also expect that my ammonia/ nitrate or nitrite levels would be high?


hello, i need help. my betta fish was just killed by my filter, but i fixed it and thats fine, but i has to unplug it for about 30 minutes and i think that lowered the ph in my aquarium. it was at 7.6 before and now its at 6.0 . i got a new betta and it now has i platinum betta and a black mystery snail. how can i make it 7.0 fast without moving any of the animals, and how can i keep it there?


Baking soda or crushed corals will work fine to increase the pH, but you should not make the change fast. Take some time to allow the fish to adjust. To quick of a change causes stress on the fish.


interesting ! Thanks for information !


I don’t understand why you’d remove the fish while raising the pH. Wouldn’t moving them from low pH water to high pH be effectively the same as raising the pH of the water they’re in? If anything I would expect raising the pH of the water they’re in to give them a better opportunity to acclimate.


It does need clarification, it is not necessary if the pH is slightly off target, it would cause more harm than good. Nevertheless should the pH be way out of the acceptable range, it is advisable to move the fish into a more neutral environment to allow for a quick and more dramatic way to resolve the problem.


if you up the ph too quickly hen it will most likely kill them

Hi I have a 50Ltr tank with neons and guppies. I have a driftwood with a plant growing on it that I have had for ages. Recently this is causing Ph to fall to 6. I removed the driftwood and have increased the Ph to 6.8 with a neutral regulator. GH is 120ppm which I am slowly raising and KH is low at 50ppm. If I increase the KH would it counteract the low Ph caused by the driftwood? Thanks


Driftwood lowers the pH mainly be releasing tannins which soften water/ lower pH. Tannins can cause a brown/ yellowish discoloration. You can soak the driftwood in water, changing water daily, boil it, or replace it with a pre-treated version of driftwood.

Ok thanks for that- appreciate the advice


I recently just got a gold fish and I tried addying the baking soda to increase the PhD level how long will it take for my fish to stop gasping for air at the top?


Not sure if pH is the problem … check for ammonia

Cody Kwallek

Was recently checking my fish tank for different substances to ensure that it was in healthy working order. When I got to pH however, I found it was alarmingly basic, possibly around 9-9.5!!! Anyone have some ideas on how to make the pH lower?? Thanks in advance!
Cody 🙂


After making sure the test kit is in proper working condition and the fish grossly out of their comfort zone, check the list of pH influenzers above and try to eliminate the cause. Don’t forget to check your water source for pH and hardness (kH) as well.
Ways to lower the pH is to use RO water, mix it with regular water until you reach the desired level. This will, over time, lower the pH. Time being time operative word, take time to adjust the pH as to not shock the fish.


We have had our fish tank for about 3 months now. We have 10 gallon tank. Everything has been great. And now for the past 4 days the tank has looked cloudy so PetSmart told me to put water clarifier in it but it has not worked. So I tested the water and it says ph is 7.8 and alkaline and the total alkaline was moderate at 80. Last night I replaced 10% of the water when I cleaned it but still no luck. I have no idea what to do any suggestions?


There is no direct relation between pH and cloudy aquarium water. You are either experiencing white cloudiness (bacteria bloom) or green cloudiness (algae bloom). Either which is caused by excess waste in the water that the bacteria or algae feed off. Reduce feeding, increase oxygen (bacteria use up a lot) and make sure to keep up with maintenance.


My 20L fish tank Ph level changes in a week. I lower it to 7 and I check it later in the week and its up to around 7.6. Anyone know why this could be happening >


The pH is influenced by a number of factors, most of them are listed above. The main issue in your situation is likely a high carbonate hardness (kH) level. This is why most common pH adjuster do not work. You can lower kH by diluting the water with very pure water (ro water) or to change your water source. Check the kH on both the aquarium and your main water source.

Lisa Steiner

I have a 300 lt tropical tank full of fish and my ph has dropped causing the death of 3 fish in a week, what is the best way to naturally raise the ph without harming my fish.


You can use baking soda or crushed coral. Baking soda is at 1 teaspoon for every 5 Gallons (~20 Ltr) On crushed coral, place one cup in a mesh bag so you can add or remove as needed to achieve and maintain the desired pH. Once you have to correct amount you can release the coral onto the substrate.

Lisa Steiner

How is the best way to add it as can not remove the fish. Sadly just lost another one :'(

Dimitri Snowfox

Ok so i have a 55 gal tank that im planning on making into a plated cichlid tank. Currently there is crush argonite/oolite for the subrate i plan on using dirt and and peat moss as well. Is there any specific dirt that will help bring the pf down? Currently its at 8.6 but i would rather have it at 7.6-8.0 because of doing planted.


Aragonite is a crystal form of calcium carbonate and will keep your pH at higher levels. There are many varieties of plant substrates, but none will have big effects on pH, Peat moss nevertheless will lower the pH but might be hard to use as substrate.


I have a 40 gallon tank set up for for Discus fish. I have a handful of plants, although they are fairly new to the tank. My PH appears to be in the 7.6 – 8.0 range. Any suggestions on how to safely lower it? Also, I see that RO water is good. Is distilled water the same as RO?

If the aquarium setup is fairly new, wait until the cycle is completed to see where the pH will end up. If the cycle is complete, check on CO2 levels using this link
If there are elevated CO2 levels, try to air out the aquarium. Increase airflow do diffuse the CO2
After these steps, you can lower the pH by using purified water RO or Distilled, there is no real big difference besides the way the water is processed.

John hunter

I am new to the tank world but i just tested my water and i have extremely low ph and high alkaline what shold i do please help oh ya this is a cold water tank around 64 to 60 i use no heater and my room is fairly kept cool THANK U ALL AND PLEASE


It depends on what you consider low pH and high alkalinity. Some reasons why this could be is the use of buffers, in this case discontinue using buffers (pH up). The most likely issue is high levels of CO2. You can air out CO2 by heavily aerating the aquarium. You can also add some Kalkwasser which will break down the CO2 and raise the pH.

Rajan Thakur

I have 90 gallon african cihlid tank with aquarium sand and 15kgs of limestones for ph buffer but my water ph not gose above 7.9 ph
Any suggestions to raise ph upto 8.2 to 8.4


The critical point is the stability of the pH. Cichlids from Lake Tanganyika prefer a pH between 7.6 – 8.6 and the Lake Malawi cichlids between 7.2 – 8.0
In either case, your pH is where is should be, no need to mess with it.


I have a 55 gallon tank in which I had city water for my African cichlid & peacock cichlid tank and then out of nowhere they died. A bacteria formed and only 1 fish survived out of 20 and now I’m having problems getting well water to be stable to maintain the aquarium. My water is acidic in PH and very soft. The nitrate is at a .5 when it was 0 and I just had to restart the tank again. I put 2 peacock cichlid with the jewel cichlid and the peacocks both died but the jewel cichlid remains… Read more »


The pH can be raised by baking soda, crushed seashells, crushed corals, or aragonite. You can also add buffers by using Kalkwasser (lime water) which is calcium hydroxide that comes with a pH of 12

Jay M

I just set up my 55 gal planted tank and am running CO2 at 1-2 bubbles/second. The pH is down near 6. Is adding baking soda the best way to raise it?

CO2 lowers the pH, so make sure of the CO2 level. It might be too high, or sufficient with a lower injection rate. This could bring your pH back up. What you need to know is your pH and kH values, then head over to and check the table for the CO2 concentration.

Baking soda is one method, the fastest for sure. Slower but longer lasting are aragonite or crushed corals/ sea shells.


CO2 lowers the pH and is likely the cause of the drop. Make sure to check on kH as this will determine the stability of the pH

Peter m

Wow nice commets, now i know who to ask when i have a problem


Hey my PH levels in my tank have been at a steady 7 For weeks throughout the cycle…’s not all finished with the cycle but it has dropped to 6.5 and I’m worried it will drop further. I have plants and two pieces of driftwood in a 146L tank. I put CO2 in about a day ago so is that the cause? Or two much driftwood. I also have 30 fish in my tank all are small like mollies, zebra danios, tetras gubbies and two medium fish such as a pleco and a upside-down cat fish


CO2 lowers the pH and is likely the cause of the drop. Make sure to check on kH as this will determine the stability of the pH

Alfred Bon

I have saltwater tank has a reading of 0.20 ammonia, 0 nitrites, 0 nitrates and my ph level is low is there any chance to increase it i’ve added crushed coral a bit but not have been try the baking soda on it.. is my reading is safe although i’ve started it as it is and my fish are doing well. Thank you


You have to check your alkalinity levels. If the alkalinity is good, it could be a temporary shift. Marine salt mixes should provide sufficient buffering, make sure salinity is correct. The ammonia reading? Has the tank just been set up? If so, give it some time for the water to find its balance. Once complete, you can make adjustments if needed. CO2 could be another factor, try to air out the water before adding it to the aquarium.

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