Hello, and Welcome.
I'm still very new to this board, but not to fish keeping. The very first thing new fish keepers should understand is even though you may have set up a tank because it is beautiful, your entertainment comes last to the good health, and proper care of your new additions. Bravo to you for seeking advice!
Proper habitat, pristine water quality/conditions, and a proper diet are crucial to raising healthy fish. To advise you further we would need to know which species you have, how many, and the specs on your set up. (tank size, filters etc...)