How To Cycle A Fish Tank? [Nitrogen Cycle]

Cycling a fish tank is the process of establishing a natural ecosystem in which fish and plants can live and thrive. It is important to cycle a tank before adding any fish, as this will help to ensure their safety and well-being without allowing the build of ammonia, nitrates, or nitrites to dangerous levels.

There are several ways to cycle a tank, but all involve the use of bacteria to break down waste products. In this blog post, we will discuss the benefits of cycling a fish tank, when it is not necessary, and how to go about it!

What Is The Nitrogen Cycle? gif maker

The Aquarium nitrogen cycle is a very important process that must happen for a healthy tank. The good news is, that it’s pretty easy to understand and doesn’t require a lot of work on your part.

In this post, we’ll break down the four stages of the nitrogen cycle and what you can expect during each one. By the time you finish reading, you’ll be an expert on cycling your aquarium! The first stage of the cycle begins with ammonia generation. This is a repetitive cycle that keeps occurring in your tank. However, it has to be induced for the 1st time.


Ammonia Generation: The nitrogen cycle is the process by which ammonia is converted into nitrites and then nitrates. Ammonia is produced by fish waste and decomposing plants, and it is highly toxic to fish. Co2 is also produced.

Nitrite Production: The second stage of the nitrogen cycle occurs when bacteria in the aquarium convert ammonia into nitrites. Nitrites are also toxic to fish, so they need to be removed from the water as soon as possible.

The bacteria that convert ammonia into nitrites are called nitrifying bacteria, and they live in the filter media and on surfaces in the aquarium.

Nitrate Production: The third stage of the nitrogen cycle occurs when bacteria in the aquarium convert nitrites into nitrates. Nitrates are relatively harmless to fish, but they can build up to dangerous levels if they are not removed from the tank.

The bacteria that convert nitrites into nitrates are called denitrifying bacteria, and they live in the gravel and on surfaces in the aquarium.

Nitrate Removal: The fourth and final stage of the nitrogen cycle occurs when nitrates are removed from the water and so also carbon-di-oxide. This can be done through water changes, or by using live plants in the aquarium. This increases the oxygen in the water which is good for fish.

Take a look at the cycle below:- gif maker 2022 06 07T123612.990

What Is The Importance Of Cycling A Fish Tank? gif maker 3

Aquariums, and the creatures that live inside them, excrete waste. In a freshwater aquarium, this ammonia can build up to dangerous levels without a proper nitrogen cycle in place.

A properly cycled aquarium will have a beneficial bacteria colony that breaks down ammonia into nitrites, and then nitrates.

Cycling a tank is important because it allows the tank to develop a healthy nitrogen cycle, which helps to keep the water clean and reduces the amount of waste produced by fish.

There are several benefits of cycling a tank:

  • It creates a healthy environment for fish.
  • It reduces stress on fish, which can lead to healthier fish and reduce the likelihood of disease.
  • It makes maintaining an aquarium easier because there is less chance of ammonia or nitrite levels becoming toxic and harming fish.
  • It establishes a biological filter in the tank, which helps to remove harmful toxins.
  • It creates a healthy environment for your plants as it facilitates plant growth.
  • Establishes beneficial bacteria in the tank that break down harmful ammonia and nitrite into less harmful compounds.
  • Helps to keep your fish healthy and prevents the growth of algae.
  • Allows you to monitor water parameters, such as pH levels and ammonia levels, so that you can take corrective action if necessary and avoid fish poisoning.
  • Allows for the filtration of waste products and creates a stable environment for fish and other aquatic life.
  • Prevents “new tank syndrome”, which can cause fish to become stressed or die.
  • Increases biodiversity in the tank, as well as helps have a more attractive display by helping plants to thrive.
  • It helps prevent the spread of diseases and also helps the development of immunity in fish.

How To Cycle The Fish Tank? gif maker 1

Clean The Substrate And Add It To The Tank :

Gravel or sand is popular substrate for aquariums, and it’s important to clean it well before adding it to your tank.

Many people try to skip this step, but rest assured that cleaning the substrate is an essential part of setting up your aquarium and maintaining healthy water conditions. 

Fill Water:

Lay a plastic cover on the place where you fill water and add water by allowing the water to fall on the plastic cover so that it does not disturb the substrate by its force.

Once the water reaches a level where the substrate will not get disturbed, remove the plastic cover and continue filling the water. Do not fill the tank to the brim and allow a 1MM gap.

Test The Water:

Test your water for chlorine and ph levels. It’s important to make sure that these levels are in the normal range to keep your fish healthy and thriving.

By keeping an eye on these levels, you can prevent any serious health issues from arising in your aquarium.

If the water contains chlorine, make sure you add a De-chlorinator which is easily available in any aquarium store.

Then check the pH and if it is on the higher side the best natural choice is to add a few plants to your aquarium.

Add A Filter:

Wondering if you should add a filter to your tank? Wonder no more! Adding a filter is the way to go – here’s why.

Filters help keep your water clean and clear, making your tank look nicer and preventing the build-up of harmful toxins.

Plus, filters provide vital oxygen to your fish and help regulate the temperature of your tank, keeping your fish healthy and happy.

Pro Tip: Make sure that you know what type of filter you should be buying depending on the type of fish you have. For example, a beta fish needs a very mild filter. So do make sure that you consult the local aquarium store or a professional on what type of filter to purchase and then add a filter to your tank.

Add A Heater:

Adding a heater to your aquarium may seem like a pointless task, but it is one of the most important things you can do for your fish. A heater keeps the water at a consistent temperature, which helps to keep your fish healthy and immune to diseases.

Pro Tip: Remember to find out the proper temperature according to the fish in your tank.

Add Bacteria :

There are two ways of adding bacteria to your new aquarium.

The first way is to add water from another aquarium. However, it has to be done with great caution because any infection in the water can get transferred to your new tank.

The second way is a safer method, but a slightly longer method. This is by purchasing good bacteria which is available online or in the aquarium store and adding it to the water.

Add A Few Hard Fish:

Many may recommend adding a “few” fish to your new tank. However, it would be ideal to add hard fish to your tank since they will survive the new tank syndrome better.

The new tank syndrome causes fish to die from shock in the new environment. Sucker Fish, Loaches, and swordtails are good options.

Feed The Fish:

If you’re an aquarium owner, you know that one of the most important things to do is keep the fish fed. But did you know that when the fish excrete, they are also starting the nitrogen cycle?

It’s true! When the fish excrete, ammonia is introduced into the tank and the ammonia gets converted into nitrates and nitrites by the bacteria. This is when the cycle begins. Allow two to three days for the ecosystem to establish itself.

Re-test The Water:

This time you will test the water for four parameters.

a. Ammonia

b. Nitrates

c. Nitrites

d. Ph

Look at the color chart provided by the manufacturer to ensure normal levels. A comprehensive test kit is always good to have as an aquarium owner. In the event you are using digital devices, refer to the chart provided by the manufacturer.

If the levels are normal your cycle is complete. Your tank is now ready.

When Should You Cycle A Fish gif maker 5

When You Are setting Up A New Tank

Setting up a new fish tank can be a fun and exciting process, but you must cycle the tank before adding any fish. This is because a new tank lacks the bacteria required to automatically cycle the water.

This can also kill your fish because the fish enter a state of shock in a new tank which can cause death. This is also known as “new tank syndrome”.

When Your Tank Lacks A Bacterial Colony

There is no sure way of knowing whether your tank contains a bacterial colony but if there is ammonia in your tank it is very likely that the tank has a bacterial colony.

Nevertheless, if you are fish or dying frequently it could be that the bacterial colony is not sufficient and you can engage in cycling your tank. If this is your case then, you can do partial recycling of water which may better the circumstances.

If this is your case then, you can do partial recycling of water.

Ammonia, Nitrite, or Nitrates Are High

When it comes to aquarium tanks, one of the most important things you can do is keep the water cycle in check. This means monitoring ammonia, nitrite, and nitrate levels and taking corrective action when necessary.

Believe it or not, your fish will thank you for it! However, if a water change is not helping, and the ammonia or nitrate levels are really high, a water change becomes necessary.

Few Things To Know: gif maker 4

Media From An Established Tank:

Do you have an old tank you’re not using anymore? Did you know that media from your old tank can be used to cycle a new tank?

It’s true! You don’t have to go through the hassle of cycling a new tank – just use media from your old tank. This will introduce beneficial bacteria into the new tank and help to cycle the new tank quickly.

If you are wondering what media is, it’s the content inside the filter.

However, remember, media must be from a perfectly healthy tank, with no sick fish or fungus. The water must have also been clean. Also, remember media must be from the tank which has the same family of fishes.

Aquarium Salt:

If you’re looking for a way to cycle your fish tank without using chemicals, look no further than aquarium salt! Aquarium salt is a natural product that can be used to cycle your fish tank.

Simply add the recommended amount of aquarium salt to your new tank and allow it to dissolve. The aquarium salt will help to cycle the new tank and keep your fish healthy.


Did you know that plants can also help to cycle a fish tank? That’s right – plants are natural filters and can help to remove ammonia and nitrites from the water. Simply add some plants to your new tank and reap several benefits.

Plants are a great addition to any aquarium. They provide many benefits, including helping with water quality and oxygen levels. They also provide hiding spots for your fish where they can feel safe and lay eggs.

Wrapping Up:

Cycling your tank is important for the health of your fish and keeping the nitrogen cycle in balance. The four stages of the nitrogen cycle are ammonia, nitrite, nitrate, and oxygen. Ammonia, nitrite, and nitrate control are important for fish to stay alive.

By monitoring these levels with a water testing kit, you can take corrective action when needed to ensure a healthy aquarium environment. What tips do you have for keeping your aquarium cycled? Do let us know. If you have a question, please do ask. We will be glad to help. gif maker 2021 11 22T222634.326

Here's More...

More Form Our Blog