i'm at a total loss! chemistry near perfect.

My bad, I didn't see that. My reef crystals tests at 380 with a Salifert test kit. I think it is odd that his calcium is still that low with reef crystals. Is it possible that his inverts are pulling that much calcium out of the water? I would definitely double check the test kit.

 

Calcium does not get pulled out of the water. Calcium and carbonate are pulled out at set ratios.

Most of this advice is sound. Go back to the drawing board and fellow directions in steps.

Get on the calculator and see how much Mg you need to get where you want. Get it up to where you want. and test again.

Stop dosing Alk... most seasoned reefers are much more conservative with Alk... it does not need to be jacked up to 14 and will only cause problems. Suggested is 7-11... I shot for the middle of 9... absolutely nothing wrong with 8 and will keep things more stable. Let it fall naturally till it gets where you want.

Use the calculator as you did and get your Ca squared away... when you get things in balance don't dose for two or three days and then see what you consumption is and that will be your new daily dose.

Do this all SLOWLY. Nothing good happens fast in a reef. Swinging large doses just swings the other parameters and you get wacky readings.

 

Agreed.

Focus on getting Mg up and let the Alk drop. Then worry about Ca.

I like to keep my Mg around 1500 and my alk around 11 or 12. 8 is great.

Keeping my Mg there also keeps my SG around 1.027.