Before the internet, people cycled their tanks for years without knowing what they were actually doing to their fish. Now that I do know, I still cycled my tank with fish. I have a 20 gallon, and I got some water from the LFS. I bought 3 danios, because they are a hardy fish. I always over-filtrate my tanks. I over-fed the fish, and over-oxygenated the tank. I bought a placard from the store that shows ammonia, and nitrite and installed it into the tank. Whenever the amonia level stated to move toward the "dangerous side, I would do a 50% water change. Then the nitrite levels started to go spike just like the ammonia. I treated the tank the same, and did the 50% water changes. I did this probably about every 3-4 days. The fish always seemed fine, and the levels never got to the "dangerous" level on the placard. once the nitrite levels went to zero, I backed off the feeding, and checked the nitrate levels. They have been as close to zero as you can get. The fish always seemed happy and healthy, and are in my tank as I type this. I do weekly 25% water changes. I only do 25% because of how much filtration my tank has. Hope this has helped.
