In addition to balancing water temperature and pH levels and keeping ammonia out of your tank, it is also important to reduce the build-up of nitrates, the final stage of bacterial breakdown that occurs during the chemical conversion of fish waste in the nitrogen cycle. Nitrate is the end result of ammonia converting to nitrite, formed during the nitrification process, and though it is less toxic than ammonia and nitrite, it is still harmful to fish if not kept in check. Causes of high nitrates include too many fish in the aquarium producing too much waste, too many uneaten nutrients, dying plants, dirty filters, and untreated tap water. Nitrifying bacteria get into gravel and build colonies. They thrive on nutrients that form from ammonia, nitrite, and oxygen, breaking them down into nitrates. If plants do not use all the nitrates up, they build favorable conditions for an algae outbreak, which deoxygenates the water and places stress on the fish and plant life. First-time cycling tanks experience an algae bloom, or "new tank syndrome," as a result of too many nitrates.
Keeping nitrate levels ideally at 5 ppm or below, but at least lower than 10 ppm, is necessary for a healthy environment in your aquarium.You can reduce nitrate levels in your tank by cleaning the tank and replacing the water partially each week to maintain healthful parameters. By keeping nitrate levels down, algae will be kept to a minimum, the water will be clear, the oxygen plentiful, and the fish and plant life will thrive. Your regular maintenance will lessen your work and reduce your losses. End result? You will enjoy a healthy aquarium for many years to come.