I strongly recommend against cycling your tank with fish in it. Too much work keeping up with water changes to keep the ammonia in safe ranges for the fish.
Toss a few cocktail shrimp in the tank and let them decompose. Once the ammonia and nitrite have bottomed out, remove whatever is left of the shrimp, do a big water change, and start stocking. Some people put the shrimp in media bag to help make cleanup easy after you're done cycling.