Agreed. On startup, donor sand/water from an established reef is a good way to get "cultured" water into a newer setup. But water changes (unless large as a % of total volume) are not a very efficient method of nutrient export, yeah I said it. It would replace trace elements, alk, ca, etc....but IMO the bulk of nutrient reduction/transformation happens via biological means. So algae, bacteria, sponges, and the like integrate waste into our systems. Some folks with some of best reefs don't change any water.....but I know I am not exactly breaking new ground here. That being said, most of us don't have reefs that reduce waste at the same amount we add it by feeding....so we change water to help. Walt's pointing you in the right direction. Personally, water from my SPS tank gets changed with new water. This "used" water goes to my anemone prop tank and then anemone prop gets drained into the lawn (keeps the salt cost down!). The prop tank grows fistfuls of halimeda and does run noticeably less clean than my reef, but I am sure bioloads/skimmers/etc are different between the two tanks so comparisons aren't apples to apples. HTH
