I run Ca reactor without a kalk reactor. My Ph is 8.3 to 8.1 in the tank, in reactor 6.8 to 6.6. My Ca was at 450ppm, alk was 3.43, mg was 1200. I added 200gm of Mg and the alk went up to 3.89 with the ph going up 0.12 in one hour. Mg is now 1300ppm.
I was told once that Mg was the middle of the tetertater, between Ca and alk. If one wont go up but the other will, check your Mg level. I don't know if this is true or not, but it worked for me.
