Understanding "Nitrification" vs "Denitrification" Process in Aquarium

Understanding the differences between Nitrification and Denitrification process in your aquarium:

Nitrification: Ammonia -> Nitrite -> Nitrate; Denitrification: Nitrate -> Nitrogen gas + H2O

Photo from: https://www.metawater.co.jp/eng/solution/product/sewer/

What is Nitrification?

Nitrification is the natural process that occurs when the beneficial bacteria in your aquarium converts ammonia into nitrites and then nitrates. This is the first and essential stage of the nitrogen cycle. Nitrification is an aerobic process, i.e. bacteria consumes oxygen in order to carry out the process. The overall reaction of nitrification is:

Ammonia NH4 → Nitrite NO2 → Nitrate NO3.

Q: How to achieve nitrification process?

In order to achieve a stable parameter and safe environment for the fish, a continuous and stable process of nitrification MUST be establish. This can be done by choosing a suitable filter with efficient bio media, and dosing beneficial bacteria while cycling your tank.

What is Denitrification?

Denitrification is a biological process of reduction in which the nitrogen compounds, Nitrates, are released back into the atmosphere in the form of Nitrogen gas. It is the final stage of the nitrogen cycle, carried on without oxygen. Denitrification, unlike nitrification, it is performed by denitrifying/anaerobic bacteria where it takes place in the absence of oxygen and organic carbon compounds (anoxic condition).

The overall reaction of denitrification is:

2NO3− (Nitrate) + 10e− + 12H+ → N2 (Nitrogen) + 6 H2O (Water molecules).

Q: How to achieve denitrification process?

Denitrification simply means the removal of nitrate by creating an anoxic condition, i.e. with low dissolved oxygen. Under such condition, anerobic bacteria will turn nitrate into nitrogen gas and water molecules. Once achieve, the successful removal of nitrates means you may now skip your water change routine*.

Without denitrification process, the removal of nitrates can also be done easily through water change. Adding live plants will also help to absorb part of the nitrates. Some products may help absorbing or reducing nitrates, hence reducing the need of frequent water change, for example, Seachem DeNitrate, AquaForest Purifying Resin, Domin8 Bacteria.