Magnesium in aquariums

[Rodolfo Garcia]

Are magnesium fluctuations more forgiving?
My tank uses about 10ppm mag daily and it drops from 1350 to 1280 weekly. I then dose mag supp once a week the same day to bring it back up to around 1350. Is this jump ok?

 

[Randy Holmes-Farley Verified Community Expert]

I cannot believe for a second that your tank uses 10 ppm of magnesium per day. That would necessarily mean it is using more than 100 ppm of calcium per day, which does not happen ever.

I’d suggest not measuring magnesium at all. It is too prone to test errors to be optimal for dosing and it moves around a lot as salinity changes.

This has more:

https://www.reef2reef.com/threads/just-say-no-to-magnesium-testing-rmm-is-born.1017528/

 

[RedReefer904]

Regardless of what your tank uses on a daily basis, you shouldn’t only be dosing once a week. The ideal way to dose is to find out what your tank is actually consuming on a daily basis and tried to replace it at the same rate that it’s being consumed to minimize any "swing" at all. all these corals want the same thing which is stability.

 

[Randy Holmes-Farley Verified Community Expert]

Regardless of what your tank uses on a daily basis, you shouldn’t only be dosing once a week. The ideal way to dose is to find out what your tank is actually consuming on a daily basis and tried to replace it at the same rate that it’s being consumed to minimize any "swing" at all. all these corals want the same thing which is stability.

That is not true for magnesium. It depletes so very slowly that once a week is more than often enough for it in any tank. It does not hurt it to dose more often, but it is not needed.