After we have set up our new fish tank, I am sure the first thing we wanted so much to do is to start putting the goldfish in. If we do that, we will be putting that goldfish into a stressful environment with the risk of dying… unless it is for sacrificial purpose.
This is because the new tank is undergoing the Nitrogen Cycle process which releases toxic compounds into the water. As it is a new setup, there aren’t enough nitrifying bacteria (the good guys) to break those damn toxic compounds down to non toxic.
This is why we need to cycle the fish tank. We need to let these bacteria establish their colonies first in order for the fish tank to be safe for our fish. They grow mainly in the filter media and substrate. There are less amount of them on the decorations and in the water.
Curious on how these bacteria look like to our naked eyes?
This is a picture of some filter media in one of my established fish tank’s filter. The brown stuff are the good bacteria. Yummy looking right? 🙂
Before you start to cycle the fish tank…
Make sure you have test kits that are able to check for Ammonia, Nitrite and Nitrate. The test results will let you know how the cycle is going.
Note: The following paragraphs contain affiliate links. For more information, please visit my disclosure page.
I am using API Freshwater Master Test Kit. I like this master test kit because besides having test kits for Ammonia, Nitrite and Nitrate, there are also test kits for pH and high range pH. These kits are in liquid form.
To do the tests, take some water out from the fish tank and put it into the clean glass test tubes that are already provided in the master kit. Each test tube is used for one test. Give your test kits a nice shaking, then follow the instructions on how many drops of the test kit that you need to add into the test tube for each test. Cover (also provided) the test tube and shake it nicely. Leave it for around 5 minutes and then compare the result with a color chart that comes with the master kit.
OK, so how to cycle the fish tank?
Firstly, please turn on your filter and let it run.
The important step in cycling is to have Ammonia in the tank as it is food for the good bacteria to grow. This can be achieved through 2 methods:
- Cycling with fish
In another words, this is the method where you sacrifice a fish. You will need to use a healthy fish as you do not want to introduce any disease into the tank. So you put that sacrificial fish into the tank, and the wastes from this fish will turn into Ammonia that will kick off the cycle. However this poor fella will be subjected to the toxic compounds until the cycle is completed (i.e. if it’s tough enough to go through all those). You will need to do frequent water changes (25%-50%) when you see the fish’s condition deteriorate.
- Cycling without fish
This method is simulating the situation where Ammonia is introduced into the water. No live fish sacrifice is required. This can be done by putting excess fish food or dead shrimps into the tank. When they decompose, Ammonia will be released into the water.Another way is to add pure Ammonia directly into the tank. Do make sure it is pure Ammonia with no additives. Additives may leak poison into the tank. Use this calculator to determine how much pure Ammonia you need for your tank size to achieve the ideal of 3ppm concentration.
After doing whatever necessary to have Ammonia in your tank, the next thing to do is wait. The cycling process typically takes around 1-2 months to complete.
How to know whether the cycle is working?
During this period of time, do regular water tests for Ammonia, Nitrite & Nitrate to determine which stage your cycling is at. Do these at least once a week.
- Stage 1: Ammonia increases –> due to the Ammonia introduced via fish wastes, decomposing fish food/shrimp or the pure Ammonia that you’ve added.
- Stage 2: Ammonia slowly decreases, Nitrite slowly increases –> Nitrosomonas bacteria are already breaking down Ammonia
- Stage 3: Ammonia decreases, Nitrite decreases, Nitrate increases –> Nitrosomonas & Nitrobacter bacteria are already working together to break down the toxic compounds
- Stage 4: No Ammonia, No Nitrite, Nitrate increases –> Your bacteria colonies are already established. Cycle completed.
After the cycle is complete, do a big 50% water change to remove Nitrate and your tank is now safe for your goldfish.
Is there a way to speed up the cycling?
Yes, if you are able to get hold of some existing bacteria colonies. You can add them to your filter or into your fish tank and it will speed up the bacteria growth. You can get them from:
- Filter media or substrate from healthy established tanks.
Do not clean these filter media or substrate. Take them as they are (i.e. along with those brown yucky stuff)
- Bottled bacteria products in the market.
I have tried one of the brands before but it didn’t work for me. Anyhow if you are getting this, make sure to check the expiry date!
I have used some filter media from my other established tank to cycle my goldfish tank. It took around 2 weeks to complete cycling.
Yay!… can I add my goldfish to the tank already?
Yes, you can… but don’t go crazy and add a big bunch into the tank in one shot. Be patient and add one or two at a time. Give it around a week’s interval for the good bacteria to adjust to the bio load of the fish tank.
So once your fish tank is cycled, the colonies of bacteria will continue to grow and keep your fish tank safe for your goldfish; unless majority of them are removed or destroyed. This can happen by washing your established filter media or substrate with chlorinated tap water. If this is the case, you will need to cycle the fish tank again.
So these bacteria are very important in fish keeping. Take care of them and they will take care of your goldfish!