Troubles raising KH

[Douglas]

My biggest problem with using a reef calculator like that, is detemining the exact water volume.

Display size + sump size, - the rock amount, to get exact or approx water volume.

I tried that, and added the amount requested, but still get a low KH reading.

[Proteus]

Can I ask what your testing with. API. hanna

If your using API. I have bought one that must have froze at some point and gave me off readings

Could it be so high that your getting a bad reading