[cheseboy]

Hi, I am looking at the diffrent kinds of Supplements for fish and crustaceans. Would I need to worry about Magnesium for crustaceans or does regular water changes keep the levels fine. I don't need to wory about the calcium levels either, for crustaceans right? Since regular water changes should keep the levels in order? Some people say don't add anything you can't test for. Iodine?