Corals color can be based on many things. Mostly light spectrum and nutrient levels in the tank. A higher kelvin light like 15-20k will lead to better coloration. Depending on the coral poor color can also be a result of to high of nutrient levels. Dosing iodine IMO is never needed and you should only dose if needed and you test for it. Calcium, alk and mag are all used to build a corals skeleton. They don't really help with color
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