is a tap filter really necessary? i've been using tap water and treating it for the past 6 months, but i've come across this and was wondering if it would be better for the fish. also, i'm planning on getting a reef tank within the next 2 months, i was wondering if i would need the filter for that also. i found a tap filter at Petco for $75....looked on Dr. Foster & Smith and they have it for $30 lol, stupid Petco. I know an RO unit is better and all, but they are much more expensive. just looking for some input! thanks!