Very high alkalinity!

[JohnK]

Agreed, don't dose anything. Keep doing water changes to bring the alk down. You could add Ca and in turn trigger precipitation which would make both levels drop, but I don't think that's advisable.

 

[Moe_K]

Rule of thumb in this hobby: don't make sudden changes.

 

[SeaCilla1212]

My calcium is like 300 or 350

 

[nemodan]

http://reefkeeping.com/issues/2004-05/rhf/


Excess of bicarbonate depress Ca levels

Read the article of the link