Regular partial water change. This is clasical and still absolutely valid method, it dilutes many undesireable substances that can't yet be detected in tests.

Healthy vegetation also contribute significantly in reducing aquarium nitrate level or at least can slow down its increase considerably. Many aquarists prove that it's not difficult to establish and maintain natural balance over a longer period of time even in small aquarium. This type of aquarium is planted tank : dense planting with aquatic plants from the beginning and low population of fishes.

Filtering aquarium nitrate with special filter material on the basis of ion exchangers, which extract nitrates from the water. However, this method can only prolong water change intervals to 4 weeks instead of the usual 1-2 weeks.

Nitrogen depletion method. This method uses certain types of bacteria which are able to respire the oxygen bound in the nitrate molecules, thereby producing Nitrogen gas into open air. The low-oxygen environment that needed for this method is created by net bag containing nutrients. The net bag reduce water flow, causing lack of oxygen which forces the bacteria - with the aid of the nutrients in the bag - to use the oxygen bound in nitrate molecules to breathe. So, nitrogen gas escapes into open air and aquarium nitrate is removed.

Do not removed rotten deposits from aquarium substrates. This deposit can create low-oxygen area where bacteria can breakdown nitrates.