One of the most critical elements every goldfish owner must understand is how to cycle their tank.  This is necessary in order to provide a stable environment for their aquatic community and prevent health issues that result from New Tank Syndrome, a serious and often fatal condition caused by unbalanced water parameters.  Achieving stability in a tank’s ecosystem can only be done through the nitrogen cycle, the process which is covered in detail in other articles.

In this post, we are going to cover how to cycle your goldfish aquarium so your goldfish can thrive.

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What You will Need for Cycling

You will need to have an appropriately sized tank that has set up with substrate, a filter, and some decorations for the fish to hide in once they arrive. The tank should also be filled up to the brim with water that has been treated by a conditioner that removes chlorine.

You will also need an ammonia source to kick-start the cycling process. This can come from fish waste (produced by fish), degrading material such as food or plants, or straight from a bottle (as sold in hardware stores for cleaning, called Ammonium Chloride).

I recommend fishkeepers use this pre-measured liquid ammonia for cycling fish tanks.

It’s the most reliable (and safe) method.

You will also need a water testing kit so you can keep track of your progress in the cycle and know when it is safe to add fish.

The last thing you will need is a source of beneficial bacteria to start your colony.  I recommend ATM Colony Pro.

Starting the Cycle

feeder fish (comet goldfish)

Image Credit: BurjoStudio, Shutterstock

Once you have everything ready, you must get that filter running. The cycle cannot complete unless a filter is continually at work.  When it comes to introducing an ammonia source, some people will purchase cheap “feeder fish” (which are really small common and comet goldfish) sold by the thousands in pet stores to get that ammonia going.  However, some have raised objections over subjecting them to the very dangerous conditions of an uncycled tank and prefer to use the liquid version. (It may also be worthy to note that feeder fish may introduce harmful pathogens into the tank and cause the goldfish you want to keep for pets to come down with disease.)

If you choose to use live fish, the ammonia will start to accumulate from the time you place them in the tank.  If you choose to use the liquid chemical, you will need to put it into some kind of a container that dispenses by drops.  Also, be sure you keep this well labeled and out of the reach of children!  It may also be helpful to note that the latter method enables you to crank up the temperature (86 degrees Fahrenheit to 95 degrees Fahrenheit) which will speed up the process, but without frying any fish.

The Cycling Period

Keep the tank well oxygenated to promote the accumulation of good bacteria. This can be done by ensuring that the flow of the filter has a some distance to fall before touching the surface of the water, making more water agitation.  An airstone can also help with this.

Before adding the ammonia source, you will need to “condition” the tank with beneficial bacteria which can be derived from the filter media of a previously established tank or from the pet store in a bottle (I use Top Fin’s Beneficial Bacteria, but a similar brand will do fine).  After waiting at least an hour, you may add one drop of ammonia for every gallon EACH DAY or introduce your ammonia-producing fish (in which case you will not need to add ammonia by hand).  Yay, you say, I will have to do less work if I use live fish.  Sorry – daily water changes of at least 20% are required to prevent your fish from dying and stopping the cycle abruptly before it finishes, so that actually might prove to be more work.

After a few days, if you are using the liquid chemical version, test the water successively every day for ammonia.  You will probably see a large spike of it on your first test.  This is normal.  Continue to test daily and look for nitrites.  They might take some time to appear, but don’t forsake the adding of the ammonia!  After you get a reading of nitrITES, watch your successive readings for nitrATES.  The ammonia level will begin to decrease until it reaches 0ppm.

You will want to continue adding ammonia even after it reaches 0ppm until the day before you get your new fish.  When this happens – and it might take up to 8 weeks – you will  be able to add your new goldfish friends.  Adding them before the ammonia level goes back to 0 can jeopardize their lives, so please make sure your tank is safe before adding pet goldfish.  It is recommended to do a large water change (50 to 90%) the day before getting them, and do not add a large batch of new fish all at once or you risk spiking up the ammonia again… one at a time is best!  After that, you may do weekly water changes and add beneficial bacteria on occasion to counteract an ammonia spike from, say, overfeeding.

Now you know how to cycle your goldfish tank!  Hope this has been helpful to your fishkeeping journey.