The nitrogen cycle

The nitrogen cycle

The most important chemical process occurring in water is the nitrogen cycle. This cycle ensures that the water remains healthy by converting waste products into building blocks.

In its simplest form, the nitrogen cycle looks like this:

1. Fish excrete waste products as a result of metabolizing (digesting) food. Most of this waste product leaves the fish through the gills, in the form of ammonia (potassium).
   
   
2. The toxic ammonia in the water is converted into nitrite by nitrifying bacteria established in the biological filter. This requires a lot of oxygen.
   
   
3. The toxic nitrite is then converted by other types of nitrifying bacteria, with the help of oxygen, into the (virtually) non-toxic nitrate .
   
   
4. Nitrate is a building block for plants . When plants have sufficient nitrate levels, nitrate levels will be acceptable.
   
   
5. Plants provide food for the fish directly (direct consumption by the fish) or indirectly (for example via herbivorous animals).
   
   
6. The fish digest their food and excrete waste products in the form of ammonia. The circle is complete.

In reality, the entire nitrogen cycle is much more complex. It involves a world of chemical processes. However, this most basic example will help you understand the process in broad terms and thus make it controllable.

The part of the nitrogen cycle that converts ammonia to nitrate via nitrite is called the nitrification process. I'll discuss this further in another article:

In nature, a complete nitrogen cycle occurs. The number of fish adapts to the "self-cleaning capacity" of the habitat. This means there is a natural balance. There will be proportionally much fewer fish than in our ponds.

In our generally overpopulated ponds, this biological balance is often hard to achieve. We will have to take measures to keep the nitrogen cycle going. For example, we have a biological filter This is necessary to provide sufficient space for the nitrifying bacteria. We will also need to change the water to prevent nitrate levels from rising too high, among other things. Finally, we will need to feed the fish, as they don't have enough natural food available.

Yet the nitrogen cycle remains vital in our ponds. It's therefore crucial to keep it functioning and make optimal use of it ( with a few tools ). Sufficient water changes, a sufficiently large biological filter, and good feed are key to achieving this.

Author: Joop van Tol (Koitoday)