How to Cycle a Fish Tank


Understanding how to cycle a fish tank can make all the difference in creating a healthy small eco-marine system in your home. Aquarium owners who are just new to this hobby will soon realize that cycling your fish tank will yield happy and healthier plants and fishes. Seasoned and expert hobbyist always does this as part of their preparations.

What is Cycling?

Cycling is the act of generating a filtration system for your tank to ensure that there is the presence of a bacteria colony. This rids the toxic wastes so you can make sure that the aquatic life you have has a conducive environment to live in.

The main objective of cycling your fish tank is to establish a bed of bacteria in your natural filter to remove the toxins produced by the fish’s metabolism.

These bacteria will then be responsible for digesting the ammonia from the waste, converting it to Nitrite. Note that Nitrite on its own is dangerous than ammonia. But the bacteria will eventually turn this to Nitrate, which is less harmful to your fishes.

A fish tank undergoing the cycling process is mentioned as having a “New Tank Syndrome”. If your tank has not been adequately cycled when the time comes that you must add in new fishes. The environment could be so toxic that it can lead to your newly added species’ death.

How to Cycle Your Fish Tank

You have several options on how to cycle a fish tank. You can do the cycling with fishes inside your tank and the other one san the fishes.

Fishless cycling – this is a safer option since your swimming creatures will not be exposed to high nitrite and ammonia levels. This method will not risk the lives of your fishes.

Timing plays a critical element when you are doing fishless cycling because you must be done before you need to put in the fishes.

A critical factor in a fishless cycle is you are accountable for adding the ammonia to the aquarium to imitate your fishes’ waste production. You must continuously add ammonia to the system so that the cultured bacteria won’t die from food scarcity. To do so, you must leave your aquarium tank empty for months.

Once you have cycled your filter, you can slowly add some fishes to the system.

Note that fishless cycling will not cycle the aquarium straightaway. Reproducing the biological colonies in an aquarium regardless of size will take time, and so does the whole process of fishless cycling. Rest assured that doing this will make it a more effortless and more seamless experience for your fish.

Fish-In Cycling – this approach, on the other hand, is preferred by both newbies and veteran fish enthusiasts. Looking at an empty aquarium for months can be frustrating. Nobody can wait that long for good bacteria to start developing. Thus, the reason why fish-in cycling is invented.

When initially setting up your tank, only put in a few fishes. Some would recommend a ratio of one fish to ten gallons of water. It is best to select the hardiest and most vital fish for the first batch. Guppies are an ideal choice.

For your first batch of swimmers, lightly feed them for the first few weeks and slowly increase their food intake. This will directly impact their waste production and it helps with the bacteria. It would be best if you feed the fishes lightly at the start because there won’t be enough bacteria to handle all the wastes being produced.

Measure the quality of your aquarium water using a water test kit. Do this every day, and every time there is a noticeable quantity of ammonia. If the results go above 0.2ppm, partially change the water to rid the accumulated toxic and replace it with clean water.

It is considered as a complete cycle when you can feed the fishes the average amount of food every week while keeping both the nitrite and ammonia levels at 0ppm and the nitrate level of 0-39ppm.

Cycling Using Plants – if you want a more creative approach, then cycle using plants is the best way to do it. Not only does it help your natural eco-system biologically. But it adds to the visual aesthetics of your aquarium.

Rather than looking at an empty and boring tank with little to zero fish at all. You can put in some aquatic plants and then put your energy into growing them with the help of good lighting, fertilizers, and substrate.

Live plants consume nitrogen waste better than bacteria, so this makes a very great option for you. Once the algae exhibit growth, then your tank cycling is done.

Tips When Cycling Your Tank

When adopting a fish-in cycling method, don’t use goldfishes. When in a tropical aquarium, goldfishes are vulnerable to catch a disease. So the entire tank can easily be infected and diseased. Note that goldfishes are cool water fishes and would not be able to adapt to the warm temperature.

If your aquarium is smaller. You can include Cherry Barbs, White Clouds, and Zebra Danios for the first batch of fishes in a fish-in cycle.

Cycling with a lot of fishes without enough bacteria can cause your tank to develop a nasty smell.

Having too much fish in your tank while the cycle is ongoing can cause an overproduction of wastes. This can stress your fishes and may cause them to get sick and die.


How to cycle a fish tank? Aquarium cycling is not an easy task. It needs plenty of time, patience, and effort. You must let Mother Nature take its course, and all you can do is wait and provided reinforcements to help speed up the process.The wait is worth it, though, because you can be confident that as you add new fishes to your marine ecosystem. You give them a higher chance of survival. It also, overall, impacts your maintenance routine, making it more manageable.

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