What is the Nitrogen Cycle?

6th May 2023

The Nitrogen Cycle is a vital process that takes place in every aquarium, making sure your fish have a healthy environment. It's a series of natural biological processes that turn harmful substances like ammonia and nitrite into less harmful nitrate, which can then be removed through water changes or used by plants.

Here's a quick rundown of the Nitrogen Cycle:

  1. Fish make waste: Fish create waste as they eat, breathe, and grow. This waste includes solid waste (poo) and ammonia, which comes out through their gills. Ammonia is super toxic to fish and can cause health issues or even death if it builds up in the aquarium.
  2. Ammonia to Nitrite: In a healthy aquarium, good bacteria called Nitrosomonas turn ammonia into nitrite. Nitrite is also toxic to fish, but not as much as ammonia. These bacteria live on surfaces in your aquarium, like the filter media, substrate, and decorations.
  3. Nitrite to Nitrate: Another group of good bacteria called Nitrobacter change nitrite into nitrate. Nitrate is much less toxic to fish than ammonia or nitrite. These bacteria also live on surfaces in your aquarium, often alongside Nitrosomonas.
  4. Nitrate removal: Although nitrates are less toxic to fish, they can still cause problems if they build up too much. There are a few ways to remove or reduce nitrate levels in your aquarium:

    a. Regular water changes: By changing some of your aquarium water (usually 10-25%) every week or two, you can dilute and remove nitrates from the water.

    b. Live plants: Aquatic plants consume nitrates as a nutrient source, which can help reduce nitrate levels in the aquarium.

    c. Nitrate-removing media: Some specialised filter media can help remove nitrates from the water. These are usually added to your aquarium filter.

The Nitrogen Cycle is crucial for keeping a healthy and stable aquarium environment. When setting up a new aquarium, it's important to give it time for the cycle to establish before adding fish. This process, called "cycling," can take 4-6 weeks. During this time, you'll be checking the levels of ammonia, nitrite, and nitrate to make sure they reach safe levels before introducing fish.

Understanding and maintaining the Nitrogen Cycle is the key to providing a safe and healthy environment for your aquatic mates.

TL;DR: The Nitrogen Cycle is essential for a healthy aquarium. It involves beneficial bacteria converting toxic ammonia (from fish waste) to nitrite, then to less toxic nitrate. Regular water changes, live plants, or filter media help remove nitrates. When starting a new tank, allow 4-6 weeks for the cycle to establish before adding fish.