Your new aquarium needs two types of beneficial bacteria.The first will converts ammonia into nitrite, while the other will converts nitrite into nitrate. Ammonia will be produce your fish in poo and pee. High levels of ammonia are dangerous to fish, there is bacteria that can convert ammonia into nitrite. Nitrite is actually even more toxic than ammonia, but the second group of bacteria will turn the nitrite into nitrate, which is much less toxic. The nitrate can then be removed by regular water changes.The beneficial bacteria will of course need to get started in the aquarium, and this is done by adding one or two hardy fish.The bacteria colony will take time to establish and this process takes several weeks.

You should purchase a good aquarium test kit, since while your tank is cycling you will need to test the water. The ammonia level should rise. Once the bacteria spreads the ammonia level will go down and the nitrite level will rise, as the second group of bacteria grow these level will also drop. The cycling is complete when both the ammonia and nitrite level are at zero when water is tested and the nitrate level are at safe readings. At this point it is important to do proper water changes to maintain your tank.