LEVEL OF NITRITES (NO2-)

No nitrogenous substance should pass the threshold limit in a well-balanced aquarium. As ammonia and nitrates are more difficult to assess, it is the nitrites that must be analyzed regularly. There is a colored marker commercially available, which gives a stronger color according to the amount of nitrites present. If the latter are too abundant:

• either there is a general imbalance (too many fish, too much food in the water) which entails a high production of ammonia and, therefore, nitrites;
• or there is a problem connected with the transformation of nitrites into nitrates, often a lack of the oxygen required by bacteria.

The darker the pink color, the more nitrites there are in the tested sample.

The level of nitrites, like the pH level discussed above, is a good indicator of the equilibrium of an aquarium, and it is therefore important to measure it regularly.