High Magnesium in reefTank

Has anyone had high magnesium in there tank while other parameters are good?. Are there side effects to a tank with it? Mine are at 1650. Alk is at 9.5. Cal is at 430. PH is at 8.1-8.2. How do you lower Mag? I read water changes. I use reef crystals or Instant ocean. Which salt has low mag when you mix it? This started to climb about 6 months ago. Wondering if Instant Ocean change formulas?

Are you dosing aiming that has mag as a secondary ingredient? Your tank may be using the cal and alk faster than the mag and so you are dosing for those two but also adding mag

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Are you dosing anything … sorry

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I found this comparison chart online of reef salts.


I’m dosing Alk and Cal. ESV. I am not dosing Mag.

That’s strangely high. High doses of magnesium have been used as a method for reducing hair algae, but it is a fine line. If you get too high it will kill inverts. I know snails and shrimp get his first, but not sure about nems and clams.

Have you tested a freshly mixed batch of saltwater to see if the mix is the culprit?

That’s my next move Adam. Doing a water change again next week. I’m going to test for a few thing. Thanks Adam

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how old is your test kit? I use IO and most of the time i need to supplement mag. I shoot for 1450

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Test kits are new,Salifert.

Mike have you lost any macro algae from your fuge over the last 7 months? If you have the space macro algae uses mag fairly quickly in comparison to corals. Maybe add more to your fuge or a different type.