When an aquarium has insufficient regions deprived of oxygen (anaerobic zones) or denitrification proceeds incompletely then nitrate will build-up. A too high nitrate concentration can result in unwanted algae-growth and these might irritate corals in their neighbourhood. Nitrate as such also retards coral growth. The nitrate concentration in a proper functioning reef aquarium should preferably be lower than 1 mg/L. Fish-only aquariums would usually show much higher nitrate concentrations.
Salifert Test Kit Nitrate