Cycling refers to the process of tranforming ammonia into nitrates that can be digested by plants, this is done via adding ammonia and nitrifying bacteria or allowing the process to occur naturally through fish waste. As fish eat and create waste, more and more ammonia and nitrites are introduced into your water. Plants can absorb this, and turn it into food via a process called denitrification. Initially, your system will need to establish the nitrifying bacteria colonies so that this process can create its own balance. If using fish to cycle your system, you'll want to add your fish, and not feed them for the first 24 hours, and then only sparingly for the first few days. Bacteria will populate normally, or you can use starters or additives to speed up this process. You'll want to check your water daily to measure ammonia, nitrite, and nitrate levels. For healthy fish, ammonia levels should stay below 3.0 ppm, and nitrites below 1.0 ppm. Once these levels drop below 0.5 ppm for 24 hours, cycling is complete.
Since this process can be stressful to fish if ammonia or nitrite levels become too high, there is also the option to cycle your system without fish. This is simple enough, as you'll take the place of the fish waste through adding ammonia to the water yourself. Here, you can also add a bacteria starter, or wait for the colonies to form on their own.
