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What is “cycling” your fish tank? Why is it important? Instructions for how to do-it.

If you have never owned a fish tank before, you may be overwhelmed by the sheer volume of information available on the subject. You have probably heard terms like “water quality” and “cycling” thrown around but may still be figuring out what those things mean. The term “cycling” typically refers to the nitrogen cycle in the home aquarium. This is the process through which beneficial bacteria break down accumulated waste, converting toxins like ammonia into less harmful substances like nitrite and nitrate. Because ammonia is toxic to aquarium fish, it is essential that the nitrogen cycle be established in your tank – without it, your fish could become very sick or die. Because the nitrogen cycle is so important, it is one of the first things you should learn about when preparing your start your own aquarium.


Cycling your fish tank is not difficult, but it does take some time – there are also several different methods you can use. In this section, you will learn what cycling is, how you do it, how long it will take, the number of fish needed, and much more!

What Is Cycling The Tank?

Unfortunately, many people have never even heard of cycling and if they have, many ignore it. However, if you want to ensure your fish live in a healthy environment, it is imperative.

The goal of cycling a fish tank is to establish a bed or colony of bacteria in your biological filter to help eliminate toxins made by the fish’s metabolism.

The bacteria grown will then digest the ammonia from waste, turning it into Nitrite. Although Nitrite in hard water or water with a high pH level is actually more toxic than ammonia, the bacteria in your tank eventually turn the Nitrite into Nitrate which is relatively less harmful to the fish.

If the water in your fish tank is not changed on a regular basis, the Nitrate accumulates and becomes harmful, causing fish to stop eating and becoming stressed. Additionally, the growth of algae is accelerated. Therefore, it is imperative that you follow the cycling process and maintain a clean tank (which regularly removes nitrates) for the health of your fish.

A tank that is in the process of cycling is often referred to as having “New Tank Syndrome.” If the tank hasn’t properly cycled by the time you add your fish, it could be a toxic environment resulting in the death of your fish.


One way to cycle a freshwater fish tank is to start with a small number of relatively hardy fish. As the fish eat, they will produce waste which will supply the nutrients beneficial bacteria need to grow and reproduce. To do this properly, we have provided guides for you to follow:

To cycle your fish tank, start with the following steps:

Begin with the smallest number of fish possible – generally two to three small fish per 10 gallons. Choose the hardiest fish you can find – examples may include guppies and mollies, among others.

Goldfish are not ideal fish for tank cycling. One reason is that goldfish kept in a tropical fish tank are much more susceptible to disease, meaning the tank can easily become diseased (Goldfish are cool water fish, and are not meant to be kept in tropical fish tanks that require warmer temperatures). Finally, the type of goldfish typically used for cycling are feeders. These fish are different from top quality goldfish and can carry diseases.

In addition to the fish mentioned, other good species for a smaller tank would include Zebra Danios, White Clouds, and then Cherry or Tiger Barbs. If you have a fish tank that is 10 to 20 gallons, five fish would be adequate.

One of the most important things is to remember to limit the number of fish with which you cycle your tank. If you cycle the fish tank with a large number of fish, you could have devastating results. For example:

There would be a high production of excess waste, causing a great deal of stress to the fish. When this happens, chances are you will have fish die and the risk of disease rises significantly.

Water problems would increase dramatically during the cycling process

When you cycle with a large number of fish, the tank will develop a very unpleasant odor

Other Options

In recent years, methods of “fishless cycling” have become increasingly popular. Some hobbyists suggest that using fish to cycle the tank may actually be cruel since it involves subjecting the fish to an environment that can be considered toxic and unhealthy. There are, however, just as many hobbyists that support cycling a tank with fish as those who support fishless cycling. Methods of fishless cycling may involve “seeding” the tank with fish food to provide nutrients for beneficial bacteria to grow. Another option is to add live bacteria to the tank to jumpstart the nitrogen cycle. To learn more about fishless methods of cycling your tank, read this article.

You are viewing this post: RateMyFishTank.com. Information curated and compiled by Congofishes.net along with other related topics.

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