Introduction to NitrateAmmonia, produced by fish as a waste product is oxidized by aerobic bacteria in the biological filter: first to Nitrite (NO2-) and further to Nitrate (NO3-). In nature a complete nitrogen cycle exists, where plants utilize nitrate as a food source, thus maintaining the very low Nitrate level found in unpolluted water.
In the aquarium we create a one way system rather than a nutrient cycle. The plant growth is mostly insufficient to use up all the Nitrate introduced by the fish food. In most aquariums, especially in marine aquariums, Nitrate will slowly accumulate, so that unnaturally high concentrations are reached.
In the reef aquarium, corals and other invertebrates react distressfully to high Nitrate levels and will eventually die. Nitrate will also act as a nutrient for plants that we do not desire. High Nitrate levels cause the development of blue-green algae (Cyanobacteria) and hair algae. Fish may eventually become stressed and weakened by the NO3- pollution, which makes them more susceptible to parasitic infection, such as white spot.
The Nitrate concentration should be tested every week. This is especially important in the marine aquarium. In a reef aquarium the Nitrate concentration should be kept below 20 PPM, but one should always strive for a zero reading, as all coral reef dwellers are adapted to these low levels, which have been stable over millions of years. Although freshwater and marine fish can tolerate levels over 100 PPM, concentrations like this form a stress factor for the fish and will undoubtedly stimulate the growth of algae.
Recommendations
To prevent the build up of high levels of Nitrate
Keep the fish density low.
Stimulate plant growth (in the marine aquarium, higher algae like Caulerpa`s, but also soft corals will efficiently use Nitrate).
Remove detritus, dead plants and other dirt.
For the marine aquarium use Nitrate free Salts like Red Sea Salt to perform regular 10% water changes. The use of Protein Skimmers such as Red Sea’s Berlin or Prizm skimmer will remove some of the waste material before it can decompose to Nitrate (and Phosphate).
