From my own experience and without journals or proper observation notes, I found that my first saltwater set-ups (this time around, using LR, not going back to pre-LR days) suffered badly from "new tank" syndrome when I was using local water and chemical conditioning. I purchased an inexpensive DI filter that connects to a faucet and noticed healthier tanks. With my RO/DI set-up I have only had one problem that I think was water related and suspect it was the need for replacing my over-used RO filter (I opened it up out of curiosity and the inside was 2/3 covered in red, slimy, very fine mud). I have changed out the substrate in several tanks and did not even have a hickup in the water parameters. A lot, I think, depends upon the water in your local area. Ours has to be filtered before it gets used at all because of the red mud, Thales has home access to very good water and can filter with extra carbon and DI without the RO (still doing it this way right Richard?).