Basic Fish CareFreshwater

Cycling a Fish Tank

Cycling a fish tankSo, you’ve set up your tank, the filter and heater have been running for a couple of days, now what? Depending on who you ask, you may get completely different answers. Some people say to throw some fish in, others say leave the tank empty for about a month. I’ve lost count of how many fish tanks I’ve set up in my life, but I can tell you what I do when cycling a fish tank. First I’ll explain what cycling a tank is, then I’ll walk through the different options to cycle a fish tank, and lastly I’ll tell you what I’ve done to quickly and effectively cycle my fish tanks. Click here to jump right to that part of the article.


Nitrogen Cycle

Nitrogen Cycle

First, what does cycling a fish tank even mean? Essentially cycling a fish tank refers the nitrogen cycle, which sounds fancier than it really is. The nitrogen cycle is made up of three main stages: ammonia, nitrite, and nitrate. Beneficial bacteria breaks down the harmful chemicals, to less harmful ones. Ammonia is the most harmful of the three, and is produced mainly by fish waste. Bacteria breaks down the ammonia and turns it into nitrite. A different bacteria then converts the nitrite into nitrate, completing the nitrogen cycle. While you can’t necessarily speed up the cycling process, you can speed up the time it takes for your tank to be ready to have fish added to it, but more on that later.


Method 1: Fish In Cycle

I’ll start by saying that I don’t recommend this method at all; however some people think it’s the only way to cycle a fish tank. A fish in cycle essentially means adding fish to your tank before the beneficial bacteria has built up. The bacteria need ammonia for food, so by adding fish, their waste becomes their food source. The problem with this method is, the ammonia builds up faster than the bacteria can grow and break it down. So what ends up happening is, the water in your tank becomes toxic and can kill or harm the fish in it.

Some people who use this method, also perform water changes every other day to help remove the ammonia in the tank. This will work; however it’s a lot of work and can actually prolong your cycle process. By doing such frequent water changes, you are removing the food for the bacteria which means they won’t multiply as quickly and it will take longer for your fish tank to stabilize. Considering there are better alternatives, I avoid this method entirely.


Method 2: Fishless Cycle

Knowing what a fish in cycle is, you can probably guess what a fishless cycle is. For those who don’t like guessing games, you don’t add fish to the tank while it’s cycling. Without fish to produce ammonia, the bacteria needs ammonia from a different source. There are a couple of ways to introduce the ammonia to the tank. Some people use household ammonia from a bottle, other people use fish food, and other people use a piece of dead shrimp. Any of these sources will work; however I have only used the fish food method in the past.

For this you add a little fish food to the fish tank every other day until ammonia is present in the water. You should only have to add food a few times. To know for sure, you will need to test the water, either with a test kit you can buy, or by bringing a water sample to the fish store. Over the next few weeks you should notice nitrite in the water as well. You should continue to “feed” the tank about once or twice a week a very small amount just to keep an ammonia source. Without an ammonia source the bacteria would die off. The goal is to eventually have ammonia and nitrite have no reading when testing the water. This means that the bacteria breaks down the ammonia at the appropriate rate. This could take anywhere from 2 to 6 weeks for the cycle process to be complete. After this time, your tank should be ready to add fish. When adding fish though, you should be sure to stock your tank slowly otherwise your bacteria won’t have a chance to remove the ammonia fast enough.

The main drawback of this method is you have an empty fish tank until the tank is fully cycled. I’ve done this method before and as long as you have patience it will work fine.


My Preferred Method

Nice aquariumFrom my experience, there is a better way to get a fish tank ready for fish. To have water ready for fish, you need to have bacteria growing in your tank. The bacteria grows in the filter media, gravel, on decorations, etc. Because of this, I’ve found the best way to cycle a fish tank is to use stuff from existing aquariums. When I set up a new tank, I use some of the substrate and plants from an existing fish tank that I already have set up. Since many people don’t have access to mature fish tanks at home, you may be wondering how you can apply this method to you.

Fish stores already have mature fish tank set up, or possibly you have a friend that does. Ask them for a scoop of their gravel or their old filter pads instead of them throwing them away. You don’t even have to worry about if the filter pad will fit your filter, you can even just lay it on the gravel or hide it in the back of the tank for a little while.

**Any time you get filter pads or gravel from other aquariums, you want to inspect the health of the fish living in the aquarium. Make sure there are no signs of disease or ask the employees at the store to be sure.**

Buying live plants is another excellent way to introduce beneficial bacteria to an aquarium, and it’s one of the best ways to help remove nitrates from the water. You may be worried about having live plants and keeping them alive, but check out this list of easy live plants that you can add to your fish tank. That list has the hardiest plants that pretty much any aquarium can have.

You may see products that say they contain live bacteria in a bottle that you can add to your fish tank. Personally I wouldn’t waste my money with them, because they have a really short shelf life and you would probably be buying mostly dead bacteria by the time you pick the bottle up. Getting gravel or filter pads from an existing take ensures live bacteria.

Once you have the bacteria added to the tank, you can add some fish food to the tank to help produce ammonia for the bacteria to eat. In about a week you should test your water either yourself or by having your fish store test it, and you should be ready to add fish to your aquarium. After a month or so you can remove the filter pad from the tank, this will give plenty of time for the bacteria to colonize the rest of the aquarium.

Thanks for reading and learning how to cycle a fish tank. I hope you find this helpful and can shave off some time next time you set up a fish tank. If you found this helpful and would like to know other tips and tricks, including the secrets most fish stores won’t tell you, please join my mailing list.


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