Thank you all for the responses. Looks like everyones in agreement about the RO/DI.
In answer to the questions that were asked:
--I live in Fairfax, right by George Mason Univ. I'll try and update my profile
--My corals are some mushrooms, a torch, a brain, a bubble coral, a large leather, an elegance coral, and some other assorted sps. I also have a clam and a few flame scallops.
I just started the hobby about 1.5 years ago, so I'm trying to learn as I go. The system I run now is as basic as it comes. Just a bio wheel filter, protein skimmer and UV. All of which hang off the back. Its simple but, its worked well. I've basically had no problems with pests and the filters have kept the water quality fairly constant and good.
One last question, because I've been using water from my lfs, I've only really been adding Calcium and Alkaline to the tank. With RO/DI water do I need to add more nutrients to the tank?
John