121,717 45

The biggest ever problem faced by the aquarist is maintaining a constant pH level. Many hobbyists fail to understand why a constant pH level is necessary in the aquarium and what factors influence the pH reading.

Why pH is important for your aquarium

For a good and healthy aquarium, maintaining a constant pH can greatly influence the water in your tank. For instance, if your pH drops below 6, the nitrification bacteria that keep your ammonia and nitrites (toxic compounds to fish) at 0 ppm, will begin to die off.

If you don’t maintain a constant pH level, then the ammonia level of your tank will fluctuate. The total ammonia is a combination of ammonium ions (NH4+) and ammonia (NH3). The pH of your water is a major factor in the relative concentrations of these two compounds. More ammonia (the more toxic of the two compounds) will be present in alkaline water while more ammonium ions (the less toxic of the two compounds) will be present in acidic water. After the cycle is completed, there should not be any ammonia in your tank anyways.

Which pH level will you maintain in your aquarium

When considering pH, you should know which pH you will maintain for your aquarium. For example, discus fish love to live in a high pH level, 7.0 maybe the optimal pH level. The same fish will likely thrive at a constant level anywhere between 6.6 and 7.4. and, for their breeding, you should keep 6-6.5 pH level. For a marine aquarium, you should keep a level that is higher than 7 pH level. In other words, a constant pH of 6.6 is better than a pH value which fluctuates between 6.6 and 7.0, even for a fish that prefers a 7.0 reading.

How to Test Your Tap Water’s pH

Many hobbyists test their tap water right away for pH. However, this is not a good indication of your pH. To properly measure your tap water’s pH, pour some tap water into a bucket and place an air stone in the bucket to agitate the surface. Then let this bucket of water sit out for 24 hours. After this, test the water for its pH. It is then a good idea to check it after 48 hours to see if there is any additional change. These values measured after 24-48 hours are an accurate measure of pH of your tap water.

In this time, carbon dioxide in the water causes the pH to drop. By exposing your tap water to the air and agitating the surface, you are causing a gas exchange at the surface of the water. This exchange reduces the amount of carbon dioxide in your water and causes the pH to rise. This pH will be the actual one you will measure in your tank.

If the fish you want to keep have very special pH requirements, like discus fish, and the required pH level is reasonably close to the pH level that your aquarium water is naturally buffered to, then I do not recommend you make any changes. On the other hand, if your fish have pH requirements which are far from the values in your tank, then you have to take some steps to adjust it to a more suitable level.

Check Your Test Kit

Many newbies in this hobby have this problem - the test kit they use does not give correct reading. This can be frustrating for a new fishkeeper who then thinks there is a pH problem, when actually there is not, and then does lots of things to stabilize the pH level and, ultimately, cause the fish to die. Therefore, if you are getting a reading that is either too low or too high for your taste, the first step is to investigate the test kit that you are using to see if it is accurate, or not.

Most test kits have its own life (usually 6 months). If your test kit is older than this, it may be providing inaccurate results If you are sure the kit is not out of date and that you followed the directions exactly then you can be confident that you are obtaining an accurate reading of the pH.

Ways to Raise Your pH

As stated above, it is generally a better idea to acclimate your fish to the pH of your water than to adjust your water to suit the pH preference of your fish. There are certain steps that can be done to raise the pH level in an aquarium.

Water Changes - if you do not change the water of your aquarium, the pH in your aquarium will drop. The most effective method to raise it back up to the level of your tap water is to do regular water changes. If you notice that your aquarium has a fluctuating or deviating pH then do 30-40% partial water change of your aquarium.
Vacuuming all of the uneaten food and waste will also help to counter the tendency for the pH to drop over time.

Rocks or driftwood - Add some rock or driftwood in your aquarium for raising the pH. Crushed coral is used as the substrate in many African cichlid tanks (African cichlids prefer a high pH of 7.0). Limestone and petrified coral will also do the trick. If you do not want to add these rocks, you can add a bag of crushed coral to your filter or hide some of these rocks behind the rocks you do want to showcase. For a discus aquarium, you cannot keep rocks whereas you can keep driftwood.

Aeration - Increasing the oxygen concentration in your water will serve to drive down the carbon dioxide concentration. As discussed above, less carbon dioxide translates to a higher pH. Therefore, you can increase the aeration in the tank to raise the pH.

Baking soda - Adding baking soda will also raise the pH, but if you add baking soda once an just forget it then its purpose is not served yet. So you have to add baking soda in your tank constantly. You also need to be careful not to add too much at one time and cause a severe spike as this could kill your fish. It is best to gradually adjust the pH if you decide it must be adjusted. The general rule is 1 teaspoon per 5 gallons. For example, I have a 63 gallon discus aquarium so I put 13 teaspoons. Dissolve the baking soda in some water before adding it to the tank.

Chemicals - There are several commercial buffers currently available on the LFS. However, these are generally not recommended as they can lead to large spikes in your pH and usually only serve as a temporary fix. They will not in general, maintain the pH in your aquarium.

Image credit Astrid

So... what do you think? Please leave me a comment or give me a


  • MyameeGirl: Great article Achintya! I’m having some issues with my pH right now and this really helped me to understand the process. I didn’t realize that aeration was so important to pH. Very imformative. Thanks!
  • adeel khan: great article sir!!!
  • johnarthur: Very informative
  • Jase: Nice article!
    Can you suggest some natural ways for lowering ph also? I’ve seen so many folk foolishly adding ph down products and cause issues this way, so any good methods collected together similar would be great too!
  • enp542: I have an awful time keeping the proper ph in my tanks, any help will be appreciated.
    Thank you
  • Phil Saint: Hi achintya, great article. Two points id like raise. You say rocks and drift wood will raise Ph. Driftwood will NOT raise Ph it will lower it.
    Also African cichlids, especially the rift lake species would prefer a higher Ph than 7. closer to 8 would be far better.
  • achintya: agreed,suggestions accepted...
  • Ky: I scanned through your post and I didn’t see if there was a way to lower pH. I’ve read in many places that driftwood lowers, not raises. Any advice?
  • johnarthur: You are correct. The term pH is short for potential Hydrogen and is on a logarithmic scale were a difference of 0.1 can be significant. Acids have lots of hydrogen and thus very low potential for more. During the rainy season in the Amazon basin, leaf litter and fallen trees release tannins into the water. In addition to producing a stain, tannins reduce pH and hardness.
  • WeeKian: Excellent Information!
  • slay diggity: thank you that was every thing i needed to know about the subject.
  • gsxgazza: excellent information here, thank you.
  • cichlidkidd: so will the baking soda make the ammonia spike if you are in the cycling process?
  • iloveloaches: Our test kit is multiple years old. Its a liquid test kit and seems to be giving us accurate readings (the results from it compared to how they tested it a the store were identical) Should we get a new one, or use what we have??
  • lewis5628: What’s your opinion on Blackwater extract to correct pH levels?
  • Joe_450: Okay now what about lowering pH?
  • Newfishmom: I am going to tackle this but I am also on a learning curve. #1 your ph also is determined by your kh, so it would be better to leave your ph higher, if it is consistently higher, it is the fluctuations that harm the fish. The fish grew in regions around the world where they flourished due to what that area offered, however, we now ship and breed fish from all over the world. Healthy fish will adjust. What is the hardness of your water? Are the fish being harmed by the ph in any way? If not, I would do nothing. :)
  • Newfishmom: We shouldn’t be posting on this older blog, I think we should go to a current question on a new post?? Didnt notice that before I answered!
  • hahhahahaha: Copy paste from here ROFL
  • Vale: hahhahahaha I believe you will find that there’s a good chance the author of the article that you provided a link to actually copied material from this site, even if the page existed before us with other content... As you can see, that author recently updated the post.
    If you still believe this article was copied, could you please PM me with more material to support your claim? Thank you.
  • ahhahahaha: Maybe he/she updated the picture
  • JeroenW: Rather misleading and inaccurate.
    1. Most fish need a stable pH and are less concerned with what that actually is as long as it’s between 6.5 and 8.5.
    2. In general Asian and South-American fish like the pH a bit lower. African lake species and central American fish like it a bit higher.
    3. Total dissolved solids play a much, much bigger role than pH in itself. Get that right and you will have happy fish
    4. Getting rid of CO2 will hurt any plants you may have.
  • AngelB.: Amazing Info! Thank you!
  • david rodriguez: Amazing Info! Thank you! help my a lot
  • Rich H.: We have 7" long goldfish in our 120 gallon tank. We have a continual problem with high nitrates ( not unexpected considering they are dirty fish ). Any suggestions to lower the nitrates? We clean the tank and bottom often. Would baking soda help with this problem?
  • Paul Roney: Baking soda won’t help with nitrates, it will alter the ph though. Have you ever tested your water supply for nitrates? Mine has about 20 - 30ppm, I use seachem matrix and jbl micromec in my filters, it takes a while to establish but is great for nitrate reduction.
  • Rich H.: Thanks Paul, will check supply water and give that a try.
  • Ellie: My ph level for both my fish tanks are 7.6. I am tryimg to get them to get in the 7.0 area. How do I do that?
  • SeaTea161: How do you lower you P.H.
  • ray: very usefull information good tips thank you
  • Craig: My Discus were in 6-7 ph tanks,from one breeder. Another breeder kept his in 7.6 to 7.8. In my mind it is what your fish get use to. My aquarium is at 7.4-7.6. Very heavily planted. My Ph wiil stay a bit high because of water changes( I do not want any uneaten food to spoil the water).The fish are happy and eat like pigs, the plants help with the ph. My Discus will eat from my hand and out of a small net.
  • Craig: Also driftwood LOWERS ph.
    Rocks raise it.
    A combo of both looks great and equals out your ph.
    Add plants to help lower it once again.
  • WalkingMermaid: Life saving information. Thank you!
  • Discus1: My Discus seem to be very happy in 7.6 Ph. All river rock has been removed and I wiii start adding more driftwood. I will also start adding r/o water once a week. I do know the importance of Ph,but I also know how slowly I must lower it. One gallon of R/O per week with a 5-6 gallon water change should not harm my babies. (four plus inches)
    Took out my air stone last week.
    Back in the day when I first had my first batch of baby discus we didn’t even check water .....Just added R/o water from time to time.The only tank I cleaned was the Mom Dad and baby tank(20 gal. long with a sponge filter )Also used an Ebo Jager heater back when they were green...Getting off the subject =0)
    Been in fish hobby for over 40 years. I used to have 20 plus tanks in one house in Simi Valley Ca. What a ball.
  • Roger Nelson: I think you have to be careful when adding baking soda to your aquarium. The amount of baking soda that you should use depends on the chemistry of your tank most of which you may not have sufficient information. For example, I have a 10 gal fresh water tank. My tank pH had decreased to 6.0. I used about 1/4 of a teaspoon of baking soda and it raised the pH to 6.4. I hate to think a full teaspoon would have done. Many others I have talked to echo caution on adding baking soda too rapidly.
  • Peter O: Obviously adding any chemical, including a substance as benign as baking soda, should be done with great care & gradually.
    The report: raising of ph from 6.0 to 6.4 (here) by the addition of one quarter teaspoon looks very suspicious. I’d wager the testing is wrong.
    Note please that baking soda is a buffer, and very commonly used in swimming pools, where it’s regular use does not directly affect ph to any significant extent.
    There is some disagreement generally also, about whether KH adjustments should be attempted using baking soda. Carbonate ions are added but also sodium ions & NOT CALCIUM ions which is what KH is all about.
    Again I use the swimming pool analogy, if you wish to increase water hardness you add calcium chloride. Sure the swimming pool is not quite an aquarium, but the principles are well known & understood by countless pool owners who generally outnumber aquarium operators 10:1.
    Please note I am not sufficiently competent to advise using swimming pool chemicals in aquariums; I offer only the facts of of pool water chemistry control to help in understanding.
  • Devin1z: Agree with most, but from my understanding drift wood decreases the PH, not raise it.
    Also what about almond leaves ?
  • Weeoff: Very helpful. I’m having problems with almost all levels in my tank. So I’m starting from the beginning with my pH lvls
  • frustrated: good info, thank you. Do I need to worry about the hardness level? I have softened well water and I got sick of buying spring water so I started just using well water. Has lots of iron but then my plants started getting sick. I have gone back to spring water. how can I fix the hardness? Just keep doing water changes?
  • Devin1z: I have read many articles on almond leaves, they all state the leaves lower PH.
    In my 50Gal tank the leaves did nothing, used them for two months. Note I changed the leaves each week, and used six each time.
    Frustrated: Have you checked. RO Buddy?
    In the long run the water will be a lot cheaper.
  • frustrated but getting better: I think your right and the water will be cheaper than buying new plants every couple of months! Thanks for the input
  • Peter O: I think the simple lesson is: stick with the method recommended by the more experienced members posting here. Most of them have done it all & know the simplest, quickest & most cost effective (in money & time) methods.
    Always use good quality clean water preferably roof collected, but properly de-chlorinated tap water is just fine.
    Do not un-necessarily pursue pH adjustments to achieve some perceived ideal. In most cases your fish will be happy across quite a wide band of pH but of course you must monitor this & know what that acceptable band is.
    Remember every time you do a partial water change (in my case 30% change every week) you may have to adjust again.
  • twebster: You kept saying high ph 7.0, I thought 7.0 is neutral, which means neither low or high. I try to keep my tanks at 7.0.
  • Oliver0660: Try changing ph or temperature go to stor and check water
  • no longer frustrated: I don’t know what mysterious toxin was causing my plants to die, but I fixed it with a 90% water change and I ripped out the underground filter, cleaned the gravel of all the sediment and installed an Eheim filter, now plants are starting to show new leaf growth. The sediment had gotten bad, I’m not sure the underground filter was working. Once stirred up visibility was about 2", I ran 2 filters for 2 days and just kept stirring the tank and gravel.
    Thank you everyone for your help

Add Your Own Comment:

By clicking 'Submit' you agree to the Site Terms
By entering this site you declare you read and agreed to its Terms, Rules & Privacy and you understand that your use of the site's content is made at your own risk and responsibility.
Copyright © 2006 - 2016 My Aquarium Club