pH value, carbonate hardness (KH), ammonium and nitrite are among the most important water parameters. Extreme deviations from the target values can suddenly become an acute danger to life. Whenever the appearance or behaviour of the fish is conspicuous, or other peculiarities (eg sudden dying of aquatic plants) in the aquarium are noticeable, the basic water values should be checked first. For routine control, the easy-to-use test strips can be used. For more accurate results, we recommend the test of the sera aqua-test box in a sturdy plastic case. Total hardness, nitrate, nitrite, phosphate, iron, copper, chlorine, silicate and oxygen should be known by the experienced aquarist as averages in his aquarium. Checking these values every now and then is usually enough. If suspected (eg poisoning, algae problems, shortness of breath) these parameters should be examined more closely.

High levels of ammonium indicate a disturbed bacterial milieu or an undeveloped activity in the filter. Very dangerous is ammonia (NH3), which is produced at pH values above 7 from ammonium (NH4). Even ammonia values of 0.02 mg / l lead to long-term gill damage. Therefore, the pH should always be measured in addition to the NH4 value.