Depends on how bad they are at the moment, If it's your water a few weeks, to a couple months depending how bad. you just need to make sure to adjust it slowly back to what it should be to not shock the corals further. Definitely get some good quality test kits especially for the Alk, cal, and mag. Test every other day and adjust accordingly. Once you have it where it should be, test every 3-4days and see what's being depleted and how fast. How big of a tank and are you currently dosing?
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