[Long Island Andy]

Hi

I have been running sulfur denitrator's for years and really like them. Unfortunately these is a limited amount of information I can seem to find.
I having an issue with calcium increasing and alkalinity diving in one of my systems

The tank is a 65 gallon soft coral heavily populated fish reef tank. The denitrator has been on the tank for over a year. I do not dose any kalk, alk or calcium to this tank and do 20 gallon bi-weekly water changes. My calcium level is currently over 600 and the dkh is 4. I have added as much as 12ozs of alk and the dkh moves to about 8 but drops by the next day. So I figured the calcium/alk ratio was so off i'd never be able to balance so I made up 70 gallons of new salt water and did 100% water change. Water going in had calcium of 420 and dkh was 7. Well within a week calcium was almost 580 and dkh 4
Sorry for being so long winded so my question is: Can the denitrator be causing this inbalance

Thanks