Keeping the tank healthy


Waste produced by fish and other animals in the tank releases ammonia into the water. Beneficial bacterial break down this ammonia, and nitrite is an immediate product. This is part of a normal and healthy process, but nitrite can make fish stressed at levels above 0.75 ppm. At higher levels, nitrite can kill fish. To remove nitrite, additional beneficial bacteria are needed; these convert nitrite to nitrate (see below). If nitrites are too high, water changes and the addition of beneficial bacteria can decrease levels. (By Ian Bacchus, Aiden Benoualid, Davis Lail, and Max Stiles)


Nitrate is produced when beneficial bacteria break down nitrite. Nitrate should be kept as low as possible in the tank – always below 50 ppm – and can be reduced by the addition of plants and by changing the water.


The optimal pH of a freshwater tropical fish tank is between 6.8 and 7.8. Keeping an optimal pH level helps reduce stress on organisms within the tank, help them be more resistant to diseases, and allow for them to reach their growth potential. (By Alana Hennon)

Carbonate hardness (KH)

This refers to the concentration of carbonate and bicarbonate in the tank. A higher KH value means the water will be more resistant to pH changes. 70 – 140 ppm is an ideal KH range for many tropical community tanks.

General hardness (GH)

General hardness measures calcium and magnesium ions in the tank. The ideal range of general hardness is similar to that of carbonate hardness, although livebearers like guppies thrive with higher general hardness levels.

Chlorine (not included on test strip)

If tap water goes into the tank, AquaSafe must be added to the water. AquaSafe has a measuring cap built into its lid, so measuring the right amount is easy. (By Ian Bacchus, Aiden Benoualid, Davis Lail, and Max Stiles)


For a tropical tank, temperature should be between the mid-70s and 80 degrees Fahrenheit. The temperature of a fish tank is important because it is important in keeping your fish comfortable and healthy. (By Anna Bourassa)