piranha tank

How To Do a Fishless Cycle of an Aquarium

A very important step that you have to go through before you introduce any fish to a new aquarium is to make sure that it goes through the “cycling” process. This is the process of establishing bacteria colonies in the fish tank and setting up a biological treatment system for handling ammonia wastes produced by fish. Read on if you plan on setting up a new piranha tank soon, or any other fish tank.

Because an aquarium is a closed environment, when fish excrete, there is nowhere for the waste to go other than stay in the tank. If the waste, which contains ammonia, is not eliminated one day you will wake up and find your aquarium has become a cesspool.

The ammonia substance is toxic and greatly affects the lives of your fish, which is why it’s important to establish bacteria colonies in your filter. These colonies break down the ammonia substance into nitrates, which are less harmful and also provides a buffer against a rapid rise in the toxicity of ammonia. There are various methods that can help achieve this, but for the purpose of this article, we will only discuss fishless cycling.

What is Fishless Cycling?


The term “fishless cycling” refers to the method of cycling the aquarium without the use of any fish, unlike other methods where hardy fish known as ‘starter fish’ are added to the aquarium. This process has been called so many names: nitrification, biological cycle, break-in cycle, start-up cycle and/or nitrogen cycle. This cycling is often done for new aquariums, but older aquariums can also go through the process as well. Knowledge of this process is vital, and failure to undergo this process will lead to great loss of fish.

Preparing Your Piranha Tank


Before you start the cycling process, you’ll need to get a few things ready. Start by setting up all the equipment ahead of time to make sure you don’t introduce anything new after the fact. This includes setting up the fish tank (of course), filtration system, heater, air pump, water conditioners, air stones, etc. You are also going to need a source of ammonia, and a liquid test kit. Make sure everything is running and that the filtration system is in working order. For the ammonia, stick with the pure forms, which include ammonium chloride or ammonium hydroxide.

Important note: Ensure that the tank is well oxygenated as the bacteria will require oxygen. Also ensure that the ammonia used is free from any additives and perfumes, and do not use conditioners that remove ammonia in treating the water.


Once you’re all set up, introduce the proper amount of ammonia that is required to raise its concentration to 4-5ppm. (See label for instructions as this depends on the size of your aquarium). Do NOT add more than you need, thinking that the process will be quicker, because it won’t.

After a few weeks the ammonia will be consumed by the first group of bacteria that will grow and then convert it to nitrite. This form of ammonia is still toxic, but in another few weeks, a second group of bacteria will develop to convert the nitrite to nitrate. The various stages of conversion should be monitored and a constant source of ammonia should be provided at every point of change/conversion.

Until you introduce your fish to their new piranha tank, do not stop feeding the tank with ammonia.

Advantages & Disadvantage of Fishless Cycling


One of the most obvious and significant advantages of the fishless cycling process is the fact that you don’t “lose” any fish during the process. Using feeder fish increases the chances of disease and/or parasites; and if this is the case could affect the aquarium. Fishless cycling eliminates that potential problem.

As much as it has its advantages, there are also disadvantages associated with this cycling method. One of the disadvantages is that it costs more compared to just having to use fish (the cost of the ammonia, cost of water test kit and so on). When decayed fish food is used, this may not contain as much ammonia to colonize sufficient population of bacteria and also it leaves behind phosphates as by-products.
When you have a sec, check out our FUN STUFF section for other interesting piranha-related thingamajigs (or is the politically-correct word thingamabobs?) like merchandise, games, etc. I’ll keep adding more in the upcoming months. Also, you can sign up for our NEWSLETTER to keep up-to-date on the latest information about our friendly neighborhood tough guys. PiranhaGuy Out.


  1. Interesting post. I’ve always done the fish cycling myself. Probably just out of habit I guess. Haven’t lost a fish yet! 🙂

    1. I’m glad you haven’t lost any. I’ve done both in the past, but lately whenever I have to set up a new tank, I just do the fishless cycle. No particular reason why I switched other than I wanted to try it out and just stuck with it. 🙂

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