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Water Chemistry

Questions of Chemistry

(The First Tank Guide)

This is a big one. There are all kinds of chemicals that you could buy to put in your aquarium, however, most of these are unnecessary.

What Chemicals Are Recommended for an Aquarium?

Probably the only two I would recommend for the beginner are a dechlorinator and an Ichthyophthirius (Ick or Ich) medication.

What About pH?

The most common chemistry questions I get are about pH. Either someone has used a pH buffer to try to adjust the pH in their tank, and has had disastrous results, or someone is trying to figure out how to adjust their pH unnecessarily. Other people are trying to troubleshoot pH changes or differences between the pH in their source water and their aquarium water. Many people don't seem to realize that most fish live in water with a wide range of pH, and very few fish require any specific pH.

Don't I Need an Ammonia Remover?

The second most common question I receive about chemicals for the aquarium is in regard to ammonia eliminators and ammonia detoxifiers. Like pH adjusters, chemicals to remove or neutralize ammonia are unnecessary and are likely to cause more problems than they solve.

What About Bacteria Boosters to Jump-Start the Cycle?

I also get a lot of questions about bacteria boosters and why many people don't seem to get any benefit from them—or seem to have disastrous results from using them, even if they only use them once or twice. Even though bacteria boosters are not really chemicals, I thought this would be a good place to list them...

How About Algae Destroyers?

Many pet shops sell algacides - algae poisons - to try to control algae growth in an aquarium. Though these may work in some cases, the side effects usually don;'t make them worth while, and there are much better ways to control algae in your fish tank.

OK, How About Water Clarifiers?

Though many people have problems with water clarity in their fish tank at one time or another, water clarifiers rarely work, unless there wasn't a problem in the first place. Proper aquarium maintenance is the solution to the problem of cloudy aquarium water, not some chemical additive.


Medication, when properly used, can be beneficial. However, when improperly used, medicines can be disastrous for your fish and your tank. use medication with caution, and preferably under the guidance of a veterinarian.

What Is a Dechlorinator?

Many people also have questions about dechlorinators or chlorine neutralizers and how to dechlorinate the water for their aquariums.

What Do You Need to Know About Aquarium Chemicals?

As a general rule, you don't want any chemicals other than a dechlorinator. Before you consider purchasing any chemicals for your aquarium, make sure you can answer these questions:

  1. Why am I adding these chemicals?
  2. What does the chemical do for me and for my aquarium?
  3. What are the side effects of the chemical?
  4. What do I do if the chemical doesn't do what I expect it to do?
  5. What happens if I do not use the chemical? Is there actually any drawback to not using it?
  6. How will this chemical interact with other chemicals I am using in the tank?
  7. Does this chemical address any need in the tank or for the fish?
  8. How do I know that the chemical did what it is supposed to have done for me?
  9. How do I know if the chemical is not working or is having a negative side effect?
  10. How do I correct for over action of the chemical?
  11. Can I overdose my fish on this chemical? how much does it take?
  12. Will this chemical interfere in the short term or in the long term with my filtration?
  13. Will this chemical interact with any medications I may need to use or prevent me from using medications (or some type of medication) at some time in the future?
  14. If I'm using chemical filtration, particularly carbon, will that remove this chemical from the water before this chemical does whatever it is this chemical is supposed to do for me?
  15. If I am correcting something with this chemical, what is it that I am correcting? How do I know that that thing is wrong I the first place and needs corrected?

If you can easily answer and understand the question, the answer, and why to ask the question in the first place, then you may want to consider using some other chemicals in your aquarium. Otherwise, you (and your fish) are probably better off without the chemical.

"We recently purchased a 50 gallon aquarium at a garage sale, and used your page verbatim on the set up and introduction of fish. We have had excellent success. Thank you very much for this valuable information. (It was twice as good as any of the books we purchased.)"
November 15, 1998
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"Great Site! My wife and I are setting up our first tank and your site has been a great help. Thanks for your advise and hard work!"
August 5, 2003
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