You need to be aware that a lot of bacterial supplements do not instantly cycle the tank. The nest ones are Dr Tim's One & Only and Tetra Safe Start. If you really want to use one, I would recommend using it to speed up a fishless cycle rather than risking fish.
If you really do want to use fish, you need to test for ammonia and nitrite every day and do a water change if either read anything other than zero. Even if the instructions on the bottle say not to do water changes, do them or the fish will suffer.
If you really do want to use fish, you need to test for ammonia and nitrite every day and do a water change if either read anything other than zero. Even if the instructions on the bottle say not to do water changes, do them or the fish will suffer.