Denitrification
The biological process that converts nitrates into nitrogen gas. It occurs in anaerobic conditions (without oxygen) within live rock, deep substrates and special filters.
Detailed explanation
Denitrification is the final step of the nitrogen cycle. Facultative anaerobic bacteria (such as Pseudomonas and Paracoccus) convert nitrates (NO3) into molecular nitrogen (N2) which evaporates from the water. This process removes nitrogen from the system without the need for water changes.
It occurs naturally in oxygen-free areas: the interior of porous live rock, the deep layers of the substrate (Deep Sand Bed), areas with very slow water flow.
In marine aquariums the Deep Sand Bed (DSB) of 10-15 cm of fine sand creates ideal conditions for denitrification. The first centimetres are aerobic (nitrification), the lower layers become anaerobic (denitrification). The problem is that a poorly managed DSB can release hydrogen sulfide (rotten eggs) if disturbed.
Sulphur based denitrators (Aqua Medic Sulphur Denitrator) use sulphur as an energy source for denitrifying bacteria. They work but require precise flow regulation.
Biodegradable carbon pellets (NP BioPlastics, VSV) feed denitrifying bacteria and reduce both nitrates and phosphates. They are dosed in the filter and consumed slowly.
Bio-pellets are popular in marine aquariums. They are used in a flow-controlled reactor. Bacteria grow on the surface of the pellets consuming nitrates and phosphates. Excess bacteria is removed by the skimmer.
In freshwater aquariums, denitrification occurs in the substrate and in very slow flow filters. However, plants are much more efficient at removing nitrates than bacterial denitrification.
Coralia Lab monitors this parameter with AI diagnostics. Tank Score alerts you when a value moves outside the recommended range for your aquarium.
Try AI diagnostics for free