Hi I am JimmyA. I am just starting a freshwater tank -- 20 gallon. I am doing a fishless cycle. I am using the Ace Hardware ammonia. I hope it works out ok. I'd like to add some plants later and then I need to select some fish. What is best? How many fish can fit in a 20-gallon tank? I know I have lots to learn. I have a carbon filter. I stuck some medium behind my carbon, hopefully that will help get the bacteria going.