Hign Magnesium? Salt?

[Rob_Reef_Keeper]

Tank parameters.
Tank - 58
CA - 440
Alk - 7.8 Dkh
Mag - ~1500
Ph - 8.1-8.3

Ive being trying to raise the Alk to be in balance with the CA at 440. Been using Reef Builder.

I measured a freshly mixed batch of Oceanic salt.

CA - 550
Alk - 7.7 Dkh
Mag - 1650

Questions:

Is the Mag that high a problem?
Is that the reason I cant raise the Alk?

I will probably switch salts again but dont know what to try next.

I used tio use IO and that was another mess on the opposite side of the scale.

CA - 260
Alk - 8 Dkh
Mag - 800

When using the IO I could never get the CA over 320, even when using turbo calcium and/or B-Ionic or Kalk.

Any other salts more inline?

How can I lower the Mag beside water changes with a salt thats low in Mag?