That and it's just a carbon filter, so it's not going to remove the chlorine, nitrates, or phosphates. R/O water really is the way to go.
Also, I see you've got a Prizm skimmer on a 72gallon tank. You should seriously get a better skimmer before you stock any additional fish. Its a highly inefficient skimmer, and despite RedSea's claims, it is NOT enough for anything over 30gallons unless you've got an insanely low bio load.
Former advisor and planted tank geek...life's moved on though.