Build up of nitrogenous waste, detritus, and impurities in an aquarium cause fish to stress and can lead directly to disease and possibly death of your aquatic wildlife. An aquarist’s understanding of the nitrogen cycle is key to maintaining a healthy aquatic environment.
1) Nutrients entering your aquatic setup are the beginning of the nitrogen cycle. Nutrient contributing factors are fish population, feeding, dead and dying plant matter, terrestrial contaminants (e.g. snails, slugs, and insects), and a variety of airborne contaminants (e.g. dust, leaves, and insects).
2) The natural decomposition of nutrients turns directly into ammonia, a toxic component to wildlife.
3) The heart of the nitrogen cycle are nitrifying bacteria which convert ammonia to nitrites.
Freshwater species: Nitrosomonas sp.
Saltwater species: Nitrosococcus sp.
Nitrites are considerably toxic to wildlife and plants.
4) Then additional species of nitrifying bacteria convert the nitrites to nitrates.
Freshwater species: Nitrobacter sp. & Nitrospira sp.
Saltwater species: Nitrococcus sp.
The nitrates are toxic in extremely high concentrations but are also an excellent aquatic and terrestrial plant food.
5) Nitrates accumulate in your aquarium but there is a limited amount absorbed by live plants (freshwater) or corals (saltwater). In a saltwater setup there is an additional step in this cycle called denitrification. At this stage there are bacteria that will break down the nitrate back into nitrogen gas and water.
6) As the nitrate level increases, so does algae growth, taking away from the beautiful aesthetics of your aquarium. If you need further understanding of algae, please refer to… Dealing With Algae: Freshwater.
7) Gravel vacuuming (freshwater aquariums and ponds only) combined with weekly to bi-weekly water changes will keep excess nutrient levels down in your aquarium.