Tap water?

[DanG]

If you get some Prime (http://www.jlaquatics.com/phpstore/s..._ID=sc-prm0250) to remove chlorine and chloramine, you should be fine. You will want to use something to remove phosphates (macro algae, chemipure, phosphate reactor, etc), but other than that, you're fine.

I've got a 70g reef tank that's perfectly healthy and I'm using tap water with prime.