How to cycle a Fish Tank – Easy for Beginners

Fish are indeed wonderful creatures with beautiful appearances. Moreover, they are unique pets that live in water, a contrast to all other land and flying pets. As such, many people seem to enjoy having fish as their pets while others make money out of it. Whatever the reason is, it is important to pay attention to details needed to raise fishes properly. An aquarium or a fish tank is one of those necessities. Fish tanks are enclosures filled with freshwater that is usually made of glass used to maintain aquatic organisms.

Setting up your aquarium for the first time can be a confusing task yet rewarding when done. It is important to prepare a healthy environment for your fish where it can thrive, and you can do that by cycling your fish tank. There are a lot of different ways to do fish tank-cycling successfully. In this article, you will learn more about this and how you can do it on your own.

What is the Nitrogen Cycle, and why is it important?

The nitrogen cycle is a process in which nitrogen goes through the atmosphere, land, water, animals, plants, and bacteria, all living and nonliving things. It is a repeating cycle of natural processes that is crucial for all living things. In plant growth, nitrogen is essential for it to thrive. Too little nitrogen available for plants will result in low crop yields. Plants cannot survive without it. Nitrogen is also very crucial for us humans too. The air that we breathe is made up of 78% nitrogen. It enters our body during respiration and helps synthesize proteins, growth-impacting amino acids, hormones, the immune system, and brain functions.

“Cycling” in reference to fish-tank signifies the conditions that contribute to ammonia conversion to nitrate. It is a process of creating bacterial colonies that control your nitrogen cycle. When you feed your fish, it releases waste referred to as ammonia. The waste is then consumed by plants and bacterias to make the water cleaner and safer for your fish to live in. This is why it is important to cycle a fish tank to ensure that the ecosystem in which the fish lives can process ammonia without harming them.

There are various reasons why the nitrogen cycle is crucial for all living things, and here are some of them:

  • Certain bacterias utterly eradicate decomposing plants and animals during the course of ammonification. This significantly helps to keep the environment clean in a natural way.
  • Nitrates and nitrites are let out into the environment due to the nitrogen cycle’s natural process, which allows the enriching of the soil by providing nutrients required for cultivation.
  • Nitrogen is needed to synthesize chloroplasts present in plants, so the nitrogen cycle is essential for their survival and growth.
  • As an integral part of the composition of the cell, nitrogen is necessary. Nitrogen is the most abundant element in the atmosphere, but it is not readily accessible to plants and animals for their cells. It is because of this repeating cycle that animals can also use the nitrogen found in the air.

The Nitrogen Cycle Process

Stage 1: Oxidation of Ammonia

This process starts with waste released by the fish (also known as ammonia). Ammonia is a pungent, colorless gas that is highly toxic under usual conditions. Poop, unconsumed food, and pee are all fish wastes that emit ammonia when they break down. When ammonia levels get too high, it’s either there are more fish appropriate for the size of the tank, or the fish are fed more than they need for optimal survival.

In the tank, ammonia will keep building up, reaching poisonous levels that can be lethal for the fish. Unless a helpful bacteria forms to consume it, the tank’s toxicity level will continue to increase. These good bacteria naturally develop on their own inside a tank kept in balance, and they will consume ammonia quickly once they multiply in number.

Step 2: Production of Nitrites

The most prominent killers of aquarium fish are nitrites, so it is the most important compound in the nitrogen cycle to guard against. As the ammonia levels in the fish tank start to decrease, the nitrite levels will increase. This becomes present in the fish tanks through the incomplete consumption of ammonium ions.

A nitrogen-fixing bacteria then convert it to nitrate, which makes it mostly harmless for fishes. Once the number of these good bacteria increases, it can consume nitrites as rapidly as they are formed. You will notice that this second bacteria is present when the tank’s nitrite levels begin to decline. This is when the final stage of the nitrogen cycle occurs.

Stage 3: Conversion of Nitrites to Nitrates

You will notice in the final stage of the nitrogen cycle that as the nitrite levels in the fish tank decrease, the nitrate levels increase. Although only one letter is distinct between the two terms, it is important to note that nitrates are less harmful to fishes. The bacteria responsible for the oxidation of nitrites give off this new chemical.

Nitrates are relatively harmless chemicals, at least in limited amounts. However, if this chemical continues to build up in the fish tank, it can become toxic. Fortunately, by continuously changing the tank’s water, nitrates can be reduced back to non-toxic levels. This is why it is vital to change the water in the tank frequently.

Should I cycle Fish-in or Fish-less?

There are many ways in which you can cycle your fish tanks. Among the most common are the fish-in and fishless methods. What exactly is the difference between the two?

Fish-in Cycling

This is the most popular method of cycling a fish tank that both inexperienced and experienced fishkeepers use. A fish-in cycle is intended to expedite the nitrogen cycle, an internal three-stage mechanism in which helpful (good) bacteria are formed in the filter to keep the fish safe and healthy from ammonia. Fish-in cycling is simply a method of putting a few fishes, waiting for the bacteria to develop, and then stocking slowly and gradually over a span of months. The idea is that the waste created by limited fish numbers is enough for bacterial growth and process waste until toxic levels increase. Every new fish addition increases the aquarium’s waste load, and each time, the bacterial population increases to manage the growth. To cycle fish-in, you have to keep in mind that the filter, heater, and air pump need to work properly.


  • Owners can immediately have a pet fish after setting up the aquarium. Most individuals do not like to wait long before getting their hands on the fish.
  • The simplest method for new fish owners who do not want a complicated process


  • Suggested method for experienced owners only because this process could be lethal for the fish
  • Exposure of fish to the poisonous chemical ammonia can cause them to die if they are not tolerant.

Fishless Cycling

This cycling method has gained a lot of popularity on the Internet. The process includes putting fish food or other sources of ammonia to produce bacteria inside a vacant aquarium. This process is not recommended for beginners because many inexperienced fish keepers frequently do it wrong and fail to complete the process. Unlike the fish-in cycle, it is safer to use and ensure that the fish will be alive. Just as creating biological colonies in an aquarium takes time, so does tank cycling with a fishless method.


  • Placing the fish in the tank is unnecessary so that it won’t be at risk of being killed.
  • Less harmful method


  • It is a more complicated method than fish-in cycling that is confusing for most individuals, especially those who are new fish owners

What do I need to fishless cycle my Fish Tank?

In order to properly cycle your tank and to ensure that your fish will be able to live in a thriving and healthy environment, you will need the following:

Aquarium Test-Kit

A test kit for an aquarium is used to evaluate an important water parameter. It is essential when it comes to fish tank cycling because it allows you to test and see if there is any imbalance in water parameters. Keeping the balance and ensuring that you have a healthy fish tank by using a test kit can avoid future algae control issues.

Our recommendation: Tetra EasyStrips 6-in-1 Aquarium Test Strips

Read more about it here: Best Aquarium Test Kits.


Adding 100% pure ammonia with no additives can promote growth responsible for the oxidation of bacterias such as ammonia, nitrite, and nitrate. To test if the ammonia is suitable for use, shake the bottle and see if the bubbles disappear quickly. If it does, then it’s good to use. If it doesn’t, it means that surfactants are added to the chemical.

Our recommendation: Austin’s 00051 Clear Ammonia Multipurpose Cleaner – 64 Ounce


Tap water is most commonly used in fish tanks. However, this contains chloramine and chlorine. Both chemicals can kill the beneficial bacteria needed for the oxidation of ammonia, nitrite, and nitrate. Adding an effective water conditioner will dechlorinate the water inside the aquarium, making it safe for the good bacterias and the fishes once they are added. Make sure not to put too much of this chemical as it can kill the beneficial bacterias present in the fish tank.

Our recommendation: Seachem Prime Fresh and Saltwater Conditioner

How to cycle your Fish Tank

To cycle your fish tank the fishless way, follow the steps below:

Step 1: See to it that the Aquarium is all set up

The first step is one of the easiest and can also be enjoyed by the entire family. To start cycling a fish tank properly, it is important to set up the aquarium. First, make sure to place the aquarium out of direct sunlight. To accommodate the filter, leave at least 5″ of space between the wall and the fish tank.

After that, add a sufficient amount of gravel that is already cleaned with clean water. Next, fill the tank with water and make sure that it is free of chlorine using a dechlorinator, as mentioned above. Lastly, ensure that all the electrical equipment such as the filter, heater, substrate, and air pump are switched on to encourage good bacterias to grow and make the cycling process faster. The first step is one of the easiest and can also be enjoyed by the entire family.

Step 2: With a Test Kit, check the Water pH.

pH refers to the measure of alkalinity and acidity of water. Many fish species can thrive in different pH conditions, but some species can only survive within a specific range. When the water’s pH level inside the tank drops below 7, the cycling process can be disrupted, causing it to slow down or, worse, stop it completely.

Not performing this step is the usual cause of failed cycles. You can do this step with ease through the use of an electronic pH meter. See that the tank will not be left alone without testing for a while since the addition of acids into the water can lower pH levels.

Read more here: How to lower pH in Fish Tank.

Step 3: Add the correct Amount of Ammonia.

There will be no waste in a brand new tank because of the absence of ammonia to break down. As a result, you will have to do it yourself. To add the right amount of ammonia, you have to determine the amount of water inside the aquarium.

After that, check the ammonia levels in the tank every day using a test kit and wait for it to drop. Lastly, see to it that the ammonia levels do not exceed five ppm but always greater than 0. Checking the nitrite and ammonia levels daily is necessary and the testing of pH levels in the fish tank from time to time.

Step 4: Test for Nitrites.

Check the levels of nitrites in the tank with the use of a test kit. If positive results are shown, it means that you’ve been successful and the cycle has officially started. It is essential to take note that this second bacteria feeds on ammonia. When performing a fishless cycle, you will have to put ammonia in the fish tank personally.

Ensure that you will not forget to do this regularly, or else the nitrite will starve, and you will have to redo everything. Once the presence of nitrite is confirmed through the test, add half of the amount of ammonia added in the beginning.

Step 5: Check if there is already a Presence of the beneficial Bacteria.

Using your test kit, search for nitrates to ensure that the nitrite decrease is due to the helpful bacteria. You are now in the tank cycling process’s final step if results show that they are present. Even after confirming that the beneficial bacteria are present in the fish tank, it is still important to ensure that they will have something to feed on.

Like in the previous step, add half a dose of pure ammonia. You can do this every day if needed, but see to it that the levels are above one ppm. Continue to do the test until both levels of ammonia and nitrates drop to zero after a full day. When that happens, the nitrogen cycle in the fish tank is complete.

Step 6: Ensure that the Fish Tank is fully cycled.

Unless you have reached this final stage, refrain from adding more fish to the tank. After both ammonia and nitrate levels reach zero, add a full dose of pure ammonia and wait for another day. If results show that the levels remained at zero afterward, the fish tank is already fully cycled. The whole cycling process can take up to eight weeks at most, so you need to be patient.

Can I cycle my Fish Tank with Plants?

Cycling a fish tank with plants is possible. Using plants can easily make the aquarium into a natural ecosystem. Instead of leaving the tank bare while waiting for the ammonia levels to drop, you can immediately add aquarium plants and make sure that they will grow by paying attention to details such as fertilizer, substrate, and good lighting. You would want to place your aquarium in the part of the house that gets a sufficient amount of sunlight. Most importantly, in many research pieces, it is found that aquatic plants can effectively eat up nitrogen wastes. The leaves and the roots especially enhance the production of beneficial bacteria as well.

The process is completed once the live aquarium plants (or algae) produce new growth. The plants absorb ammonia and nitrates effectively and turn them into young leaves and roots. Adding a few fishes gradually, feeding them cautiously, and using a water test kit to ensure that nitrites and ammonia are at 0 ppm and nitrates under 40 ppm are also essential.

Plants help to lower ammonia levels.

Conclusion – How to cycle a Fish Tank

Deciding to get an aquarium or fish tank in the home is an excellent choice for most homeowners because aside from making the space look visually pleasing, it can also bring more life to the home. Having fish as pets can also be a source of comfort and reduce stress. Surprisingly, watching your fish tank before bed can actually calm your mind and improve your sleep quality.

Although maintaining a fish tank requires a lot of work, it is rewarding and worth it when done successfully. Through research and widening of knowledge regarding the topic and the effective execution of the steps indicated above, you will surely be able to raise fishes in a healthy and safe environment where they can thrive.


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