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Ammonia Test KIts
You might be asking yourself whether or not you should get an ammonia test kit. The short answer is Yes.
Ammonia test kits are cheap ($5-10) and will tell you whether your tank has elevated ammonia levels. This is useful in two circumstances. First, during the tank-cycling phase, regular testing for ammonia will tell you when the first phase of the nitrogen cycle has completed. Second, should you have unexplained fish deaths, testing for ammonia verifies that your biological filter is (or is not) working correctly.
Note: Even in an established tank, the biological filter can sometimes weaken or fail outright. Common causes include not cleaning it regularly (water can’t flow through a clogged filter, where the nitrifying bacteria reside), naively adding fish medicines (antibiotics kill nitrifying bacteria (oops) as well as disease carrying ones), having too small a filter for the fish load, etc. Be warned: If you have fish deaths and subsequently ask the net (or a fish store) for advice, the first question asked will be “What are your ammonia (and nitrite) levels?”.
Ammonia levels are measured in ppm. At concentrations as low as .2-.5 ppm (for some fish), ammonia causes rapid death (also consult cycling section for further details). Even at levels above 0.01-0.02 ppm, fish will be stressed. Common test kits don’t register such low concentrations. Thus, test kits should NEVER detect ammonia in an established tank. If your test kit detects ANY ammonia, levels are too high and are stressing fish. You probably want to take corrective action immediately.
Warning: Some ammonia water additives are incompatible with most ammonia test kits – falsely test positive for ammonia, even when ammonia is not present.
Source: users.cs.duke.edu/~narten/faq/chemistry.html