Be Careful Adjusting Your Aquarium pH

Aquarium pH

Is your aquarium pH level off the normal level?  If so, what do you do about it?  Fish Tank pH levels, like any water chemistry problem, can usually be fixed with chemicals.  The only problem is that these chemicals have side effects and they sometimes cause more problems than they help.

What Aquarium pH Level Should I Keep?

First, let’s take a minute to learn a little bit about your aquarium pH.  You fish tank water has a pH measurement of somewhere between 0-14.  A measurement of 7 is neutral, 0 is the most acidic, and 14 is the most alkaline.  I won’t bore you with any more chemistry.  You can pick up an aquarium pH meter or test kit if you do not have one already to give you your tanks reading.  The target range for most freshwater fish is 6.5-7.5.  There are exceptions to this rule, so it is wise to read up on you specific fish species.

How Do I Adjust My Aquarium pH Level?

It’s important to realize that your fish will adapt to small fluctuations of pH.  The small changes within the 6.5-7.5 range are nothing to worry about.  If you see your levels falling outside of the optimal range you will want to address the problem.  As I said before, there are chemicals available that will either lower or raise your pH level.

How to Raise Your Aquarium pH

To raise your aquarium pH I would first try a couple of water changes.  Many times this will do the trick before introducing chemicals. If you see no change after a couple weeks of these changes, you’ll probably need a pH raising chemical

Be Careful with Lowering Your Aquarium pH

Lowering your aquarium pH is the trickier of the two.  Here’s the problem with using chemicals to lower your fish tank’s pH levels.  Most of these pH lowering products are phosphate based and have a huge side effect on your fish tank.  They promote algae growth which can be more difficult to get under control than pH.  All I am saying is be careful and use these chemicals sparingly.  It would also be wise to first try some more natural ways to lower your fish tanks pH.

Some Safe Ways to Lower Your Aquarium pH

There are some alternatives to chemicals to lower you tanks pH.  Adding driftwood or bogwood to you tank can have a lowering effect.  Pumping CO2 through your tank can lower you aquarium pH.  Make sure your aquarium gravel is neutral.  Crushed corals and other substrates can raise you aquarium pH.  Using peat to lower your aquarium pH has also proven effective.

High or low pH? Tell us about it.

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24 Responses to Be Careful Adjusting Your Aquarium pH

  1. rosa hume November 1, 2007 at 4:16 am #

    pleese give me the name of a neutral gravel, and besides a fish pet shop where else can I find driftwood, bogwood and peat? Thanks!!!

  2. Eric November 2, 2007 at 7:19 am #

    Hi Rosa,

    Pea gravel is neutral substrate. Just check the bag if you are buying your substrate from a fish retailer. As for where to find the other, there are many online shops that sell those things. I would be careful buying decorations that are not aquarium ready. Take a look here for a few more notes.

  3. BEN November 23, 2007 at 7:25 pm #

    Hi There;
    I have a PH level of 5 in my aquarium and find that my aquatic plants keep dying. I read that the best PH level is between 6.5 – 7.5. Is there a natural way i can raise the PH level in my tank? I really would like to avoid chemicals. I am starting to carry out more frequent water changes and am hoping this willl cure the problem. I have heard that adding a small amount of lemon juice will increase the water PH level, is this true? Looking forward to your response! Thanks


  4. Eric November 26, 2007 at 9:55 pm #

    Hi Ben,
    Haven’t heard of or tried lemon juice. Adding baking soda will push your pH towards equilibrium. Try 1/2 teaspoon per 25 gallons of water at a time. Wait a week to test again before adding any more. Don’t forget that baking soda is still of course a chemical. The problem is that your are working with chemicals, so it will take some sort of chemical to move the values.

  5. Bill January 26, 2008 at 10:55 pm #


    I have a 29 gal tank with cichlids in it. My tank water ph is above 7.5.My test kit only goes to 7.5 so I don’t know the real ph level . Should I lower it? My tap water is above 7.5 also. My fish seem to be ok, I have read that cichlids like it around 7 or a little lower.I have also read that most of the cichlid that you buy from the store are use to having a differnt ph than what they have in the wild.


  6. chloe January 27, 2008 at 6:48 pm #

    i have a 20 gallon tank with 2 mollies,2 gouramis,and 4 red wags and my ph is at 7.8 and i can’t find a natural way to lower my ph. please help me please!!

  7. Eric January 28, 2008 at 10:26 pm #

    Hi Bill.
    Most Cichlids can handle a range of up to 7.5 or so. It depends on the particular species. You should probably do a little research on each fish that you have. Filtering through peat moss will help lower your pH if you are concerned that it is higher. You should be able to find peat moss at your local fish shop.

  8. Eric January 28, 2008 at 10:29 pm #

    Hello Chloe,
    Peat moss is the best natural way to lower your pH. Just put it in a media bag and add it to your filter. You’ll have to test the amount. Just test often to watch for change.

  9. Samantha April 1, 2008 at 11:39 am #

    I have two mollies, two tetras,and a plecostamus in a 20 gallon tank. We have tried the dissolving tablets to correct ph and we have tried the liquid. it just seems to make our tank cloudy and destroys our filter. We have a drift wood, but we are still soaking it (as the directions stated). Is there anything i can do to fix this problem? thanks

  10. Eric April 5, 2008 at 9:37 am #

    Is it too high? That’s most common. If so, try peat moss. Take a look through the comments above for preparation tips.

  11. Liz May 30, 2008 at 5:01 pm #

    Hi Eric,
    Thank you for the fish food answer. I have another question for you. My tapwater pH is 7.4 but my tank is 7.8-8.0 (it’s hard to tell precisely from the color-indicator kit). I need to get it down because I have blue rams in there that I really like and want to add some discus eventually. I have no idea why the tank differs from the tap– all I have in the tank are four fish, a big piece of wood, two real plants and two plastic ones. My gravel is coated and I do 20% water changes weekly. So why would my pH go up? The folks at my LFS, which is quite good, suggested I leave some tap water out for a few days and see if the pH changes and then if it does I should use purified water. They discouraged me from chemicals or buffers because they said those things probably wouldn’t work in the long term. I didn’t want to use peat moss because I was worried about discolored water and I am also concerned about adding too much and having a drastic fluctuation. So. What would you do if you were me?

  12. Liz June 2, 2008 at 10:20 pm #

    Hi again,
    The plot thickens. As my LFS suggested, I filled a container full of tap water and left it sitting for three days, loosely covered. The pH rose from 7.4 or so to 7.8 – 8.0. I am stumped by this, frankly, as I have had several years of college chemistry and really don’t get why the pH would change like that when it’s not like a lot of water evaporated or anything. Hmm. Anyway the folks at my LFS suggested that if this happened, I should get a $50 water purifier and use it for all of my water changes from now on. Do you think this would work to lower my pH? Thanks for your thoughts.

  13. LISA E. June 3, 2008 at 10:51 am #

    I have a perplexing and frustrating problem! We bought a 65 gall. fish tank a little over a month ago. We followed all the rules about not adding fish and we put in the healthy bacteria via bottled additives, and gravel from a pet store’s established and clear tank. We washed our gravel thoroughly and all decor is aquarium recommended. We added a very small tetra after a couple of week and a tiny rosy red. Our water has been terribly cloudy the entire time we have had our tank and still is. It is a white/gray cloudiness. We check ph and ammonia regularly. Our ammonia level spiked after two or three weeks to the danger zone and we added an aquarium remover to our filter media. It worked great and now ammonia is 0. Our ph has gone all over the place from very alkaline to now around 6.5-6.8. I put in proper ph 7.0 and it worked to make it neutral. however, it dropped again a week later and I added more proper ph 7.0. I have not changed any filter media as to not disturb the bacterial establishment. My water is so cloudy it looks awful. I got two Oscars this weekend because I was tired of looking at nothing. They are doing great, like the cloudiness isn’t bothering them at all. But, it is not pretty to enjoy and relax by. What can we do about this problem? Water changes do not help either. I am at a total loss of what the problem is. Should the bacteria not be getting pretty established after four weeks?? Please HELP!

  14. Eric June 3, 2008 at 8:28 pm #

    Hey there Liz,
    That is odd. I think your best choice is peat moss. It just has the quickest effect. Purified water or even distilled water can bring another set of problems. You lose the buffering capacity and open your water up to swift changes in pH.

  15. Eric June 3, 2008 at 8:34 pm #

    Lisa E,
    The cloudiness is fairly common with new tanks. It does seem VERY odd to have all of that trouble with one small Tetra in a 65 gal. The best thing would be to start doing some very large water changes to help clear up all of the things you bring up. 30-40% every two days until you see it clear and your chemical levels fall in line. It sounds like you might be feeding too much. There really isn’t any other waste that would cause your spikes with only one small fish.

  16. Liz June 6, 2008 at 9:49 pm #

    Hi Eric,
    Thanks for the advice. I think for now I am just going to live with the pH how it is. The rams have been in there for a month now and they seem to be perfectly happy so maybe I should just leave well enough alone.

    I had one comment for Lisa E– I looked into those proper pH buffers and they have quite a bit of phosphate in them. Perhaps some of the cloudiness you see is a minor algae bloom?

  17. Holly June 22, 2008 at 6:13 pm #

    My question is about a pond. It is about 1500 gallons with a mix of Koi , Shebunkins and Comets. My Ph is about 8.5 and is normally very neutral at 7.0. I am looking for a natural way to lower and I see you posted at one point to use Peat Moss. Would that be the same Peat Moss I use in my garden? If so, how much would I put in my filter area?
    Thanks for any input!

  18. Eric June 25, 2008 at 6:15 am #

    Hi Holly,
    You should be able to find peat moss at your local aquatic store. I would guess the landscaping peat moss is the same stuff but I’m not completely sure as I’ve never used it. As for the amount, your going to have to experiment. I’ve never had a pond or dealt with changing the pH for that much water. However much you try, just keep a close eye and test daily once you add it. Then you can increase or reduce as necessary.

  19. James July 13, 2008 at 6:32 am #

    I have done everything by the book . i set up my fish tank, left it for a week and added 3 tetras and 2 guppies. i have been removing 10%-20% of the water weekly and replacing it. A week later i bought a siamese fighting fish and it only lasted a few days so i bought another one and that only lasted two days. my Ph is 8.5 and i am trying to lower it , is the ph level of the tank causing me the problems with the siamese fighting fish ecause all the other fish are fine??

  20. Eric July 16, 2008 at 5:41 am #

    Hi James,
    Your pH is high for Betta’s. You should try peat moss to lower it quickly. There are some preparation tips in the comments above. I don’t think that would be killing your fish so quickly though. With a new tank, stress from high ammonia or nitrites is more likely. Make sure you are testing for those very frequently.

  21. Lisa July 16, 2008 at 5:43 am #

    The Siamese fighting fish are generally kept alone. I have tried to keep them with other fish, even seemingly harmless swords and mollies, and they slowly tortured the fighter until he weakened and died. They are generally a hardy species as far as the water quality goes, hey look at them in the small bowls for sell in stagnant water! They are used to still water without much aeration, but not to say that is ideal. I kept one alone and just used spring water to change his small 2 gallon tank out every two weeks, he lived forever. Basically, DON’T keep one of those with any other type of fish no matter what!! Their flowing fins are too tempting to other little mouths.

  22. Alex August 1, 2008 at 7:47 am #

    Hi, I have a problem with my PH levels. I’ve tried neutral ways many times so I went for the chemical products. My PH level was high, so I added ‘ph down’ to lower it. I did everything by mixing it in a container at first and adding the right amount and then gradually putting it in the fish tank. I then tested it to make sure it was okay, and it was perfect. I then tested it 24 hours later, and the ph level when up high again. How do I make the ph level stay the same?

  23. BEN August 1, 2008 at 8:26 am #

    Hi Alex, with the problems i have had in the past there is a number of things you can try without the use of chemicals (chemicals will reduce ph temporarily, but you need to stop the main culprite), the ideal way being to reduce the ph in a natural way so that it leaves you with a neutral balance within your tanks eco system, and would be best done at a slow rate in order not to shock your fish. I would start off with having a good clean up within the tank, clean out the gravel/substrate you have at the bottom of your tank – check to make sure there are no dead fish/plants(including rotting roots)/food etc. Try an under water hoover or any subsrtate cleaner suitable for your set up. Some say adding things like bogwood can reduce ph levels. However I did not find this worked. You are better off going back to basics. Also reduce the amount you feed your fish, feed smaller amounts every other day – they don’t need feeding every day!!! Fish get more food being fed every other day than they would in the wild so don’t go over the top. I have also had problems with nitrite/nitrate in the past which is due to the tap water quality in norfolk – farm fertilizers on the fields are full of nitrates. It is extremely expensive to filter out nitrates so is best using bottled water. I use the value bottles in tesco/netto’s. Any still bottled water will do. In your case I would do a 50% water change using bottled water, then every 2 weeks carry out a 10% water change. Also clean out your filters using old tank water not tap water. The filters build up a good source of natural bacterias within your tank so don’t kill them off. Try this out for about 2-3 months and you should result in a good tank balance, REMEMBER DON’T RUSH IT, & LEAVE THE CHEMICALS ALONE!!! Once you have the balance in your tank its best to add fish little at a time if you need to re-stock. I hope this helps, good luck!

  24. Eric August 10, 2008 at 8:43 pm #

    Alex, Great advice from Ben! Get the basics in order and the rest should follow. I also recommend to stay away from chemicals. While working on the rest, if you want a way to lower it, you can use peat moss. You can find it at your local fish shop. Put it in a media bag, play with the amount and you’ll see results. This again will only hold things short term if everything else is out of order. Either way it keeps you from stressing your fish more while you are dealing with the root of the problem.