Calcium levels over 600.......what is best to do?

[neoh]

From my understanding, high levels of calcium do not cause adverse effects on anything except on inverts. Corals can only absorb so much. With a high alkalinity, it can be a problem - but if your alkalinity is fine, I don't think there is much to worry about, except for calcification doing damage to pumps and equipment.

If you do a dramatic decline in calcium, you would also see a decline in alk.

http://reefkeeping.com/issues/2006-06/rhf/index.php

You are much more educated on the subject than I am. However; the article above might help your mind ease regarding the increase.