calcium reactors will maintain calcium levels, first you have to get it where you want it with a calcium additive also as your dkh climbs your calcium will precipitate and drop, so what i would do is add liquid calcium to get to level of 400-450 then increase bubble rate to lower ph of effluent to 6.5 and then adjust drip rate to maintain calcium levels, i have the same reactor and i'm doing 40 dpm, and my levels are bet 450-500