7-11 dKH is a range to go for with
NSW being 7dKH.
See this
article for tuning and
here (might be helplful). What I basically do for tuning is from the first article (step 3), if my Alk goes too high, note the bubble count then turn off the CO2, once back down to ~10 dKH, turn the gas back on at a lower bubble rate whole time leaving the effluent rate unchanged (trying to reduce the variables). If Alk drops, increase the bubble count.
My biggest problem when first trying to figure the Ca reactor out was I was pushing the reactor to much trying to get my Ca initially up. Once figured my fresh SW mix was low out of the pail and started fixing that in the mixing barrel, after a little tuning by recording some numbers it's been sit back and forget.