I am starting a 36 gal saltwater tank with live rock and sand, a Fluval MSF 204 filter and a sea clone prtein skimmer, the tank is still cycling, (this sunday 9/19/04) will be two week, when I set up the tank for the first time, I use tap water to mix the salt, I am not sure this is the right way to mix the water or not, a friend of mine told me that, not suppose to use tap water, suppose use purified water, and he told me to get a RO (reverse Osmosis) Unit to create purified water, I 've been doing some research at liveaquaria.com, the RO Unit cost $200 dollar, I was wondering can I use the Tap Water Filter instead, can any one please help me....