So you finally bought your first fish tank. It's been a long time in the making but now you finally have everything you need, or so you think. When you start a new tank you do need the normal equipment like a heater, filter and light. But something else you need is beneficial bacteria in your tank. This is something that can’t be reliably bought. Beneficial bacteria is bacteria that helps break down harmful buildups of ammonia and nitrate in your tank, allowing your water to stay habitable for your fish. In order to get this in your tank, it must go through the nitrogen cycle, also known as cycling your tank.
When you put you start a new tank, the water is clean. There should be no chemicals in the water. However once a source of waste is added (food, poop), when it is broken down, it will release ammonia into the tank. Ammonia is very toxic to fish and will kill them if it reaches a high amount. Once there is ammonia in the tank, that will be also broken down by bacteria, and this time nitrite will be a byproduct. So now there isn’t a lot of ammonia, but now there is nitrite in the water. This is also toxic to fish. However, when that is broken down by bacteria, it will create nitrate as a byproduct. This chemical is not harmful to fish unless it is in a very large quantity. The entire process of developing the beneficial bacteria that can break down both ammonia and nitrite will take a few weeks depending on the method you use to cycle the tank.
The idea behind a fish cycle is after you set up your new tank and let it run for a day or two, making sure the water warms up to the proper temperature and the filter works, you add some fish. How many fish you add and what kind of fish is crucial for this. You only want to have a few fish in the tank, regardless of the size. I would recommend that you only have two or three fish even for a 40 gallon tank or higher. These fish should also be a hardy species like mollies or platies. You want your first species to be hardy because they will experience swings in water quality, and more delicate fish will die in that process.
When cycling the tank it is important to test the waters ammonia and nitrite levels in the tank every day. You can do this by getting any kind of water parameter testing kit at Walmart or any pet store. If either of those levels get to 1, then you should do a 50% water change immediately. Also it is important that you do not overfeed your fish during this time. Too much waste will lead to big ammonia spikes that can kill your fish.
As time goes on you will be able to see they cycle happen by checking the ammonia, nitrite, and nitrate levels. At first everything should be at 0. But then the ammonia will start to rise. The ammonia will then start dropping, as the nitrite begins to rise. Then the nitrite will drop and the nitrate will increase. The tank is fully cycled when both the ammonia and nitrite have risen, and then fallen back down to 0 ppm. At this point it is now safe to start introducing new fish into your tank.
Some people do not like cycling their tanks with live fish because it isn’t uncommon for fish to die during this process. So instead, they do their cycle completely fishless. This is done by adding a source of ammonia without adding fish. Some people buy bottled ammonia and use small doses in the tank, while others just drop fish food in, allowing it to decompose and release ammonia that way. This process takes away the threat of harming any fish, but a lot of people aren’t patient enough to do this. They just got their tank and want to put fish in it right away. You can monitor this tank the same way as with fish, by checking the water parameters and once both ammonia and nitrite reach 0 ppm, it is safe to add fish.
Jumpstarting The Cycle
Some people claim that they have cycled a tank instantly, this in most parts is never true. Cycling a tank takes time and it takes awhile for the bacteria to build up inside the tanks filter. When cycling a tank, you are really cycling the filter. The key to doing this is patience, but there are some ways you can speed it up. The most common way is by using filter media from an established tank to help out. If you have a filter from an established tank, squeezing and swishing around the media in your new tank will release some of the bacteria into the tank. As a warning, it will make the water brown and cloudy, but that will pass with a day or two. This method has just added good bacteria, to your filter, however you need to make sure you feed the bacteria. If you just add the bacteria and don’t have any fish in the tank, the bacteria will starve and die. They need ammonia in the water to survive. So it is important that if you choose to do this, that there is enough ammonia in the water after for the bacteria to feed on.