pH in your aquarium

Aquarium pH

The most common questions about aquarium water chemistry are about pH. In almost all cases, these questions and their related concerns are unnecessary. Most fish will thrive in a wide range of pH, and different fish have different ideal pH requirements. Though some exotic fish are more particular about the pH they require, even most of these fish are only particular about pH when they are breeding – and the only bad side effect of not maintain an ideal pH or making the right pH change at the exact right time is that the fish will not spawn. Also, most of these fish, if for no other reason than the demands on the pH are not good beginner fish. Unfortunately, there is a growing trend in the pet industry to believe that the pH in a fish tank needs to be 7.0 or very close to that. In fact, nothing could be further from the truth.
Questions about pH

Most of the pH related questions I get are from someone who has used a chemical to adjust their pH and has either had no effect or has had disastrous side effects.

Both of these effects are common and expected, and, usually, they are due to the same cause.
What is pH?

pH is a measure of the acidity or alkalinity of a substance. pH is measured on a scale of 1-14 with 7 being neutral. Something with a pH lower than 7 is acidic. Something with a pH higher than 7 is basic. Water has a pH of 7 naturally, but the water you are using in your tank will be different because of the chemicals that are suspended or dissolved in the water. These chemicals fall into three categories: acids, bases, and buffers. Acids are chemicals that lower the pH, or make the water more acidic. Bases are chemicals that raise the pH of the water, or make it more basic (or alkaline). Buffers are chemicals that can ‘tie up’ acids or bases and keep the water at a specific pH. Different buffers will keep the pH at different values.
What if I Do Want to Change the pH in My Aquarium?

If you decide you want to change the pH in your aquarium, and you are lucky, then your water will not contain any buffers. This makes changing the pH very easy. If you are lowering your pH, you add an acid to the water and as this acid neutralizes all the bases in the water, the water becomes neutral. As you add more acid to the water, the pH continues to drop and the water begins becoming acidic. You can continue this until the pH is where you want it.

However, if your water contains buffers, then things become more difficult. Again, if you are lowering the pH in the tank, you add an acid which needs to neutralize the bases that are in the water as above. However, even after the bases are neutralized, the water will maintain a high pH because of the buffers in the water. You will need to add enough of your acid to neutralize the buffer. However, usually, when you are overcoming a buffer in the water, by the time you have added enough acid to overcome the buffer, you will have enough acid in the water to cause a precipitous drop in pH.

Though almost all fish are very tolerant of a wide range of pH in the water they live and thrive in, sudden and/or drastic changes in pH, as those caused by overcoming a buffer in the water, are almost always harmful. Not only to your fish, but also to your plants and to your biological filter.

Of course, in most cases buffers in the water are good for your tank for this very reason. If the pH is buffered to a specific value, then things that are added to the tank will have a harder time changing the pH, so your water will remain more healthy and stable.

Now, remember, if you are changing the pH of the water, you will need to do this every time that you do a water change, and slight variations in the treatment of processing of the water you are using can make dramatic changes in the behavior of these buffers. Also, objects in the tank can also make a big difference in how the water is buffered. This means that you cannot, reliably, adjust the pH of your water before you put it in the tank, and this, in turn, means that if you are messing with the pH in your tank that you will have to subject your fish to this pH roller coaster every week when you do your weekly water change.

And all this for a pH change that probably isn’t necessary!
Why Isn’t it Necessary to Change pH?

Remember, most fish will thrive in a wide pH range – usually from as low as a full point below their ideal pH to a full point above the ideal. Also, different fish have different ideal pH as a base for these ranges. Some fish prefer pH as low as 5.5 and others prefer their pH to be over 8.5! Remember, before you consider messing around with the pH of the water in your aquarium, there are several questions you need to have the answers to:

1. What is the ideal pH for each of the types of fish I am keeping?
2. What is the actual pH of the water I am keeping these fish in? Not just is it high or low, but what is the value on the pH scale from 1 to 14. Just knowing that the pH is above or below 7 really doesn’t tell you very much.
3. Is the actual pH within the range for these fish? (Chances are that unless the water causes burns when you wash with it, that it is tolerable for almost any fish you could get.)
4. Is there actually a reason to adjust the pH, or am I just doing it because it seems like something to do?
5. Am I seeing any problems with my fish? Have I ensured that I am providing the necessary care for the fish including weekly 10-15% water changes, regular necessary filter maintenance, proper diet and feeding, correct temperature, correct salinity, and healthy tank population? Chances are, if you are seeing problems, that one of these tasks is not being completed, and it is the cause of the problem, and adjusting the pH will make things worse rather than better.

Quite possibly, the worst thing you could do to your fish tank is mess with the pH with chemicals. The pH is going to be buffered naturally to whatever it is coming out of the tap, and is very difficult to adjust safely. Adding chemicals to the water will very often leave you with an unstable system, constantly fluctuating and ready to plummet or skyrocket as soon as you put anything else (your hand, a fish bag from the pet store, a decoration or some fish food…) in the water. I would strongly discourage anyone from trying to mess with the pH of their aquarium water unless they really need to and they really understand chemical titrations.

Again, most fish can tolerate a wide range of pH, different fish preferring different pH, but thriving in a wide range and tolerating a wider range.

I strongly suggest that only experts with a good background in chemistry mess with pH, as any little mistake is asking for disaster. I have only been in this hobby since 1980 and would not consider myself sufficiently an expert to mess with pH using chemicals…
What Can I Do to Change the pH Slowly and Safely?

If you want to lower your pH safely, add a piece of wood to the tank as a decoration or add some peat to the filter system, but be aware that this will stain the water yellow or brown for a couple of years. If you want to increase pH, add a sea shell or a coral skeleton. Remember, these will not give you immediate, overnight results, but they will introduce buffering agents to the water to help keep the pH more like you want it.
Troubleshooting pH Changes in Your Fish Tank
How Can I Figure Out Why My Aquarium pH Is Changing?

If the pH is changing in your fish tank, or if the pH is different in the fish tank than it is from the tap (or other water source), you will want to try to figure out why this is happening. Once you have figured out why your aquarium’s pH is changing, then you will want to correct the cause so that the change is eliminated.

Before you delve into this too far, however, you should understand testing, including normal cyclic changes in your tank and what you are testing for and why.
Possible Causes of pH Shift

The most likely causes of a shift in pH are:

* Something in the water source buffering the water
* Something in the tank buffering the water
* or Something you are adding to the tank

How do I Tell if Something in the Water Source is Affecting the pH?

This is probably the least likely possibility, but it is also the easiest to check, so I’ll address it first.

To test this, fill your aquarium bucket with water and test the pH. Then let the water sit for several hours and test again. If the pH has changed, then you know that something in the plumbing (for tap water) or the packaging (for other water) is temporarily affecting the pH and that the pH is reverting once it is no longer under the influence of whatever is changing it.

If the pH has not changed after a few hours, let the water sit for 24 hours and test again. It is even less likely that you would see a change in pH at this point, because most pH changes are very rapid – even instantaneous.

If the pH in your bucket of water has changed, you know what is changing the pH, and you can easily address the influence on your tank by just letting the water sit before adding it to your tank. With a little time an patience you can even figure out how long to let the water sit (usually just a few minutes).

However, if you are not seeing the large change in pH that you have observed between your source water and your fish tank, you will need to keep looking.
What About Something in My Fish Tank Changing the pH?

Check your aquarium for items normally expected to alter fish tank pH, like sea shells, coral skeletons, wood, peat, dead plants (including leaves), dead fish (or other animals), bones, lime stone, etc.

If you have anything obvious, remove it and see what the pH does with your next water change. It may be that some decoration in your fish tank is raising or lowering your pH, and you will want to remove that.

If there isn’t anything obvious, look for less obvious things. What is your aquarium gravel made up of? Is it appropriate to your tank? Some aquarium substrates, like crushed coral, are intended only for use in marine aquarium or tanks where a high pH is desired, and can have adverse effects on aquariums where a high pH is not desirable.

If it’s not the gravel, you may want to try removing decorations or other items from your tank and see if the pH is affected. you could also try removing items from the tank and putting them in your bucket of untreated tap water (from above) and see if the pH in the bucket changes over a few hours.

When checking for possible culprits in your fish tank, don’t forget to test your filter media, as some filter media, such as crushed coral or peat, could affect your pH.

Testing all the decorations and filter media in your tank can take quite some time, but is probably the most likely place to find whatever is changing the pH in your aquarium. However, in the mean time, you can start checking your aquarium chemicals and additives.
What About The Chemicals I Add to My Aquarium Affecting pH?

It is definitely possible, even likely, that something you are adding to your aquarium for one reason or another is altering the pH. It is also possible that two or more additives may be reacting with each other, or that one or more of your additives is reacting with something in your tap water and causing the pH change.

First, read the labels on each aquarium additive, and see if any say anything about changing or altering pH. They may even say this in a positive tone, as though it is nothing to worry about (which it often isn’t). If you find one that says it does (or may) alter pH, is it something you can live without? If so, try not using that for a while and see if your pH problems go away. If you cannot live without that additive, check into competitors’ products to see if one of them may suit your needs and not alter the pH adversely. Often, you really don’t even need the additive in question.

However, even if none of your additives say anything about altering pH, there is a possibility that one (or more) is.

To test this, get a bucket of your source water, whatever that is (or use the bucket of source water you already have out, if you are not testing decorations and other equipment in it), and start testing your chemicals and additives.

One at a time, add your additives to the bucket of water. Only add what is necessary to ‘treat’ the amount of water in your bucket. After you add each additive, let the water sit fro ten or fifteen minutes, then test the pH. If the pH hasn’t changed, move on to the next additive. Keep track of which additives you are adding and in what order. Once you see your pH change, you know one of the chemicals or additives necessary to cause the pH change in our fish tank.

As I mentioned above in reference to an additive that says it may alter pH, you can choose to stop using this additive or look into a competitors’ product. If discontinuing use of this additive addresses the pH problem, then your problem is solved. But it is possible tat some other chemical is also contributing to the problem, or that this additive is reacting with something else you are adding, so you may want to continue testing to see if you can narrow down te problem additives, then choose from those which to quit using.
How Do I Avoid pH Problems in the First Place?

First, keep the number of chemicals you are adding to your aquarium to a minimum, and then make sure you know what those chemicals are, why you are adding them, and that they really work. Many of the chemicals that a lot of aquarium owners add to their tank have little or no benefit, and many even have some pretty significant drawbacks. By keeping additives and chemicals to a minimum, you will probably encounter fewer problems.

Then make sure that anything you are putting in the tank won’t affect the pH and is aquarium safe and suitable for use in the type of aquarium you are keeping.

This will probably keep you out of trouble with your pH, and help keep your tank happier and healthier. providing your weekly 10-15% water changes and other necessary routine aquarium maintenance will also help to keep any fluctuations in pH under control, as well as contributing to a happy and healthy aquarium in general.

It is also important to know what pH your fish actually want, and what pH range they do well in. Knowing this will help you determine whether you even have a pH problem in the first place.