Using shrimp or fish food
One of the more popular fishless cycling methods is to buy a few dead shrimp at the grocery store, cut them up into chunks and add them to the aquarium. The shrimp decay, which produces ammonia to feed the nitrifying bacteria. There are a few drawbacks with this method, one being that the hobbyist really has no way to know how much ammonia is being produced by the decaying shrimp, and the aquarium does not look very good with dead shrimp laying on the bottom. Also, the organic material of the shrimp can cause bacteria blooms which turn the aquarium water cloudy. This method works but it takes time and patience and you will probably see a spike in ammonia and nitrite if you add a medium to heavy load of fish after the initial cycling. Note that some people use flake fish food instead of shrimp but this is not recommended because flake food does not have much organic material compared to shrimp and so does not add a lot of ammonia to the water, but you can use cut fish instead of shrimp.