im a beginner to saltwater tanks and still learning, i need to know the correct chemical levels as far as my ph, nitrate, ammonia, and calcium levels also how important are water changes and how often is that necessary, i have several corals, mushroom, daisy polyps, button polyps, toadstool leather, branch coral, and some zoos, do any of these need special attention the branch coral has recently shrunk a little and not growing to its normal size everyday also my watermelon mushroom have lost a little color. Any suggestions would be much appreciated