How do you cycle a fish tank?

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Answered by: Holly, An Expert in the Maintenance and More Category
If you've recently decided that you want to make the time, financial, and (yes) emotional investment in having an aquarium, congratulations. Aquariums are a fun and rewarding hobby.

Like most new enthusiasts, you may have already gone to the pet store and bought all of the supplies and fish for your new aquarium. Maybe you have finished setting your aquarium up completely. You've got your filter, gravel, heater, plants, and the scuba diver with the treasure chest that pops an air bubble out every now and then even. You've put your chosen breed of fish in the tank, and then....



A week later, you have found your fish have died.

What did you do wrong? Most likely, you didn't cycle your tank.

You have made a common mistake new aquarium owners will make more often than not. It is important to cycle a fish tank before placing fish into your newly set up tank.

What and how do you cycle a fish tank?



Cycling is the process of creating a biological bed consisting of beneficial bacteria for a fish to live and prosper within. A fish would normally live in millions of gallons of water. They are part of a great cycle of biological changes that makes their environment viable to live in.

For fish to live in a man-made environment, a biological bed must be made for them also. Fish produce waste which produces ammonia. Ammonia breaks down into nitrites. Ammonia and nitrites are both harmful to a fish. Without the beneficial bacteria of an established biological bed to filter out the ammonia and nitrite, your fish are poisoned by their own waste.

However, it is possible to cycle your tank using fish. If you have access to gravel and/or water from an already cycled tank, use it! By doing this you are adding bacteria to the aquarium. This will help in the cycling process. You will also need to test your water fairly regularly to check for ammonia/nitrite spikes. You should be able to find them at your local pet shop. It is actually very easy to test the water and your kit should come with directions explaining what to do.

After being sure to rid your water of chlorine, start with hardy fish that will be able to withstand the stress from cycling. Fish breeds that are good for this are tetras, barbs, guppies, mollies, and swordtails. They are also inexpensive. Do not add too many fish to your aquarium. The more fish you add, the quicker ammonia will build especially in smaller tanks.

After adding your fish in the tank, test the water the day next day and test daily if possible. When you begin seeing your ammonia rise above 0.25 you will need to do water changes. Change out approximately 50% of the water in the tank with new water. If the ammonia level is very high you will want to take out 75% of the water. Do the same for your nitrite readings. Once the ammonia and nitrite levels are at zero, your tank is cycled. This can take several weeks to a month but your tank will now be ready for those beautiful and less hardy fish breeds you've been dreaming of.

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