Low Calcium

[Restless10101]

Hey all

First time poster.

I have a bit of a head scratcher, but I cannot get my calcium levels above the 380 mark. I have a 46 gallon Tanks with (approx.) 15 gallons in sump. Here are the water parameters:

Ammonia/Nitrite/Phosphate : 0
Nitrate : <5
Alkaline : 10
PH : 8.0 - 8.1
Magnesium : 1300
Calcium : 380

I've been manually dosing my tank with 15 ml/day of C Balance (Two Little Fishies) and has maintained a calcium level of 380. Not great, but in the acceptable range. Yesterday I tested my calcium and it was 360 and the Magnesium was at 1200. Added some SeaChem Magnesium and tested this morning and the level was at 1300. Added 1/8 teaspoon of Kent Turbo Calcium and tested a couple hours later and my calcium was at 380. Added an other 1/8 teaspoon of Turbo Calcium and retested the calcium 5 hours later and had the same result of 380.

Any advice would greatly appreciated!