The Nitrogen Cycle in Aquarium – Fishtank Cycling Complete Guide

Nitrogen cycling is the key element for a healthy aquarium and happy fish. Nitrogen cycling is known by many terms such as fish tank cycling, nitrogen cycling, cycling your aquarium, etc. No matter which term you use or listen it means the same process. In this post, I’ll share a complete process of nitrogen cycling and how you can cycle your fish tank.

The Process of Nitrogen Cycle In Aquarium

The Nitrogen Cycle is the continuous process of beneficial bacteria converting Ammonia (NH3 or NH4+) into Nitrite (NO2-) into Nitrates(NO3-).

In the first stage, beneficial bacteria called Nitrosomonas consume ammonia and convert it into another byproduct called Nitrite. Nitrite is also harmful but less harmful as compare to Ammonia. These beneficial bacteria are present on every surface inside your aquaria such as aquarium decorations, substrate, and biological filters.

In the second stage, another beneficial bacteria called Nitrobacter intervenes and converts Nitrite into Nitrates. Nitrate is less harmful and toxic as compare to Nitrite. In planted aquariums, plants absorb nitrates from water to use as a fertilizer. In non planted aquariums you can change 30 to 40% of aquarium water after every 7 or 15  days to reduce nitrates levels.

Now another question that may come to your mind is:

Where does this toxic or deadly ammonia come inside the aquarium?

Ammonia is produced by decaying organic materials inside your aquarium, such as fish excretion, uneaten fish food, dead plants. Ammonia is highly toxic and deadly for aquarium inhabitants. If the ammonia level increases too much it may kill your fish. So In order to save your fish from dying you need to cycle your aquarium.

Why do You need To Cycle Your Aquarium?

Introducing newly bought fish to your aquarium without cycling can be fatal to your fish. Mainly fish poop or uneaten fish food inside the aquarium starts decaying and produces ammonia. Because your tank is not cycled there are no good bacteria to break down ammonia into nitrate. As ammonia levels spikes it causes fish death. So It is necessary to cycle your aquarium first before introducing fish or other inhabitants.

Now you are thinking how can we cycle our aquarium. How long it takes to cycle and what are the methods to properly cycle a fish tank? Now we will discuss these questions one by one.

How to Cycle Your Aquarium?

Filters are very essential for a healthy aquarium. As you know there are three types of filtrations mechanical, biological, and chemical filtration. Only biological filtration helps to keep the nitrogen cycle going and running.

Biological filter media inside your aquarium filter provides a large surface area for the beneficial bacteria to populate and colonize. The beneficial bacteria inside your biological filter need food and oxygen to live. As water passes through the media it brings ammonia (Food for bacteria ) and oxygen with it. Bacteria consume ammonia as a food source and give nitrates that are less harmful to fish.

The very first thing to cycle a new aquarium setup is to install a biological filter filled with biological media. There are many types of biological filter media available i.e bio balls ceramic rings etc. Fill your aquarium filter with any type of biological media you purchased.

In the new aquarium setup, there is no ammonia present inside the aquarium for bacteria to consume. So how you can feed colonize or populate bacteria? There are several methods to do that let discuss these methods one by one.

Fish Less Cycling

This is the safest method but very time-consuming. In this method, no fish is involved in cycling the tank so there is no risk of losing any fish.

In the fishless cycling method, you are responsible to add ammonia to the fish tank for bacteria to consume. Bacteria need an abundance of ammonia to reproduce. To do this you have to put some organic materials inside the aquarium. Many aquarists recommend putting a dead shrimp or a pinch of fish food every day to spike ammonia. As these organic materials rot it produces ammonia. Bacteria consume ammonia and start populating and colonizing inside your biological filtration. You need to continuously add ammonia so that your cultured beneficial bacteria do not die due to lack of food.

As your biological filtration starts maturing and effectively converting ammonia into nitrate you can start adding fish to your setup. Fish poop and surplus food produce ammonia that dissolves in water and polluting it. As water passes through biological filtration media beneficial bacteria consume ammonia and make water healthy again for your fish.

This is the continuous process of the Nitrogen cycle. That completely removes harmful components from water and makes water healthy for your fish tank inhabitants.

The fishless cycling method is lengthy and frustrating because no one wants to see his tank without any fish or livestock. But is the safest one.

Fish In Cycling

In this method, you can add one or two hardy fishes into your aquarium. Feed them very little so that no uneaten food is left inside the aquarium. As fish start feeding,  fish excretion inside the aquarium starts producing ammonia, and beneficial bacteria start consuming and populating. you should be very careful as ammonia spikes too much it may kill your fish. so be careful while feeding your fish.  Use water testing kits to check the water parameters and continuously monitor unless until you found no traces of ammonia or nitrites.

Bio Media From Pre Establised Tank

In this method, you can use bio media from an already established aquarium as long as that aquarium is free from any kind of diseases infection, and parasites. This will help in jump-starting the beneficial bacterial colonies in your new fish tank. You can also use gravel from an old aquarium to helps you in shortening your cycling period but you need to give some time for bacteria to be colonized.

Dual Filter In Established Tank

Another method to speed up your cycling process is to install the new aquarium filter that you want to use in the new aquarium set up in a pre-established aquarium and wait for 4 weeks for beneficial bacteria to colonize. After that shift that aquarium filter into your new aquarium. Don’t forget to add some fish to your new aquarium because bacteria need food(ammonia) to live and thrive. One more thing to note is that water chemistry must be the same in both aquariums sudden changes in water chemistry may kill the bacteria.

Commercial Products for Bacteria Growth

You can speed up the aquarium cycling process by Installing a biological filtration system. and by adding commercially produced additives powders or tablets to promote the growth of beneficial bacteria. But before adding any livestock you must check water parameters using water testing kits if you found traces of ammonia or nitrite that means your tank is not completely cycled.

How Long it Takes to Cycle a New Aquarium?

Normally it takes around two to six weeks to cycle a new Aquarium. It may take more or less than that depending on many factors such as:

  1. Which method you are using to cycle your tank
  2. How efficient your biological filter is
  3. Are you using bio-media inside your filtration system?
  4. Are you using any additive to promote bacteria growth etc?

I hope this helps you a lot.

If you need to ask any questions or information feel free to ask in the comment section. We will be glad to answer you as soon as possible.

Leave a Comment