Hi, I have upgraded my tank to a 300 gallon, if I put RO/DI water in there, after water is at 80F can I put the fish in or should it be cycled? This is for freshwater, fish to add are black diamond stingrays, peacock bass, arowana and datnoids. my current PH is at 7.8 so with the new upgrade, I decided to purchase a RO unit to reduce the PH because the water here is really bad. Thanks.