Im very new to saltwater and want to get everything i need right. The tank im lookin to set up is a 90 gallon standard. 48" coralife dual compact and a metal halide depending on coral. This will be a full reef tank with fish, such as clowns, tangs,cleaner shrimp etc. Im using RO water and a marine buffer to make Ph about 8.3. I was told by the LFS that water changes would replace minor and some major elements that are need by coral and fish. is this true?? second of all if its not, what types of additives would i need to consider for proper growth of fish and coral. Also if im doing everything wrong, tell me and ill never shop at my LFS again!!! lol. it seems as if everything he says books and websites contradict his info. im confused none the less!