Low Calcium

[Aquattro]

Always retest with a different kit when you get weird numbers. See if you can duplicate the results.

[craigwmiller]

+1 - check against another kit, both CA and Alk. It *could* be that your alk test kit is waaaaay off instead.

Further questions:
- what salt are you using? (Purple lid Instant Ocean has low ca/alk/mag)
- what salinity are you mixing it up to? (normal 'reef' would be: 35ppm == 1.0265sg == 53ms)
- what equipment are you using to measure your salinity?
- when was that equipment last calibrated? how?

[monza]

I'd guess your tank is consuming that amount your dosing. Double dose calcium for a couple days and see what that tests like.

[gregzz4]

I'll agree with 2 points

Check your kit against someone elses and if that doesn't help, try double-dosing your tank for a day to see what happens

Because your Alk is so high, I'd think you're going to have issues bringing you Cal up

And because your Mag is lowish, it may cause issues too

I'm not saying 1300 Mag is low, but your params are out of balance, so it'll take you time to get things together

If you keep having issues bringing your Ca up with your higher Alk, I'd recommend you boost your Mag
Then you may have an easier time balancing your Ca and Alk