I'm new to aquariums, and if i'd have known then what I know now, I would have "fishless" cycled. You'll have a lot less casualties, and once the cycle is finshed, you can put as many fish in there as you want.. (as many as your tank should hold that is) Now, I've been calling every pet store in houston trying to find bio-spira so i can save my fish!! (i'm nervous that they will die from the ammonia, no matter how many water changes i do ) my advice: FISHLESS CYCLE.