Can excess magnesium have ill effects?

Hey guys,

Ive been having trouble getting my coraline getting going in my tank, which
has been establised for around 4-5 months now. Infact, im seeing little to no coraline spreading.

Calcium is beeing maintaned around 400-460 ppm, KH at 9, all levels are excellent like phosphates, nitrates, etc.

So i figures, perhaps im lacking magnesium in the tank. Someone the other day told me that with a lack in mag, coraline cant utilize the calcium in the tank. I figure that's correct because my calcium does not change, wheter i add or dont.

So anyays, i started adding some yesterday, but i dont have a test kit. so im wondering if excess Mag can harm anything or upset the overal balance of the tank??

mogurnda said:

Magnesium interferes with the precipitation of calcium. When Mg is at normal levels, it helps keep Ca in solution by preventing it from being deposited as calcium carbonate. When Mg levels are too low, you will have trouble maintaining Ca above 400, no matter how much Ca you add. If you have been able to maintain Ca at 400-460, then you do not have a Mg deficiency.

When there's too much Mg, it will make it increasingly difficult for organisms to use Ca. That's a bad thing. Because Mg is easy to measure, I would recommend getting a test kit, or borrowing one, before adding any more.

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Ok thanks.

Im wondering though why my calcium never seems to drop. It's as if it's never being used. Any idea why that is happening??

Also, no matter how much i add, calcium never goes above 460ppm......