A Simplified Guide on the Nitrogen Cycle for Aquariums Leave a comment

If you’re getting started on your new fish tank, you might have heard of the nitrogen cycle, so here’s a quick guide to help you better understand the micro-organisms living in your fish tank!


The nitrogen cycle is basically how waste(from fish) is created and how micro-organisms break down the waste which in turn becomes food again(for plants).

photo taken from aquariumcoop.com.

First, we have to understand that fish waste and its by-products are made up of 3 parts: Ammonia, Nitrite, and Nitrate. These nitrogen compounds are toxic at high levels unless there are sufficient beneficial bacteria and plants to feed on the fish waste. Let’s use 3 colors to represent the 3 components found in fish waste and its by-products.

Red: Ammonia (highly toxic and burns fishes gills which limits their oxygen intake)

Yellow: Nitrite (toxic but not as toxic as ammonia)

Green: Nitrate (least toxic)

When fish produces waste, ammonia is produced. Beneficial bacterial eats the ammonia hence producing nitrite. Another type of beneficial bacterial then eats the nitrite-producing nitrate.


At the end of the nitrogen cycle, nitrate is formed which can still be toxic to your fish in high amounts. Frequent water changes and fast-growing aquatic plants such as Rotala, Ludwigia, and Water Wisteria can help bring down nitrate levels and provide a safe and clean environment for your fishes!

Have algae issues in your new aquarium? Click here to find out ways to effectively combat algae!

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