For determining the nitrite and nitrate concentration
Nitrite (NO2–) and nitrate ions (NO3–) are formed from ammonium (NH4+) as part of the nitrification process. Nitrite, which is highly poisonous to freshwater species, is produced in the first stage of the bacterial process. If the nitrification process works, nitrite is converted to nitrate in the second stage. Higher concentrations of nitrate in saltwater aquariums will end up inhibiting the growth of delicate corals. A danger posed by high nitrate content for all aquariums is the strong boost it provides to algae growth. In rare cases, nitrate shortages can also occur. Therefore, the concentrations of nitrite and nitrate in the aquarium water should be tested regularly.