Salifert Nitrate No3 Test KitWhen there are insufficient areas of a tank which are deprived of oxygen (anaerobic zones) or denitrification is not taking place properly, nitrate will build up. This can also happen in an aquarium where the biological loading on the system is causing an imbalance e. g. if there is excessive livestock for the aquarium volume or over feeding is occurring. The build up of nitrate can result in unwanted algae growth and the slowing down of coral growth.