That is a normal process in a new tank, you might get some green algea and/or hair algea next...just preparing you. Regaurdless of the water source, it happens.....its a diatom bloom. When you get a clean up crew things should clear up. I would say after the 6 month mark things seem to settle and stablize, as long as you keep up with maintenance. I started with tap also, doing water changes with RO/DI water will dilute out the tap, in time. I dont have a RO/DI unit and have been using distilled water from Wal-mart for the last year. Its a pain, but it can be used also. HTH some.