Instant Ocean is low on magnesium to begin with so it is very likely that your magnesium levels are on the low side. 1200-1300 is the target for mag. Epsom salts in small amounts is a good way to raise magnesium but since epsom salts is magnesium sulfate you would not want to use that as your sole source of magnesium due to excess sulfates. Sulfates are needed in the reef aquarium it is just that epsom salts has a high ratio of sulfates to magnesium. As long as your bubble coral is looking good then I would not stress the high alk or the magnesium levels for now. Your tank is still very new and your bioload is light. Are you begining to get coraline growth on your glass?
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