Quote Originally Posted by NaCl_H2O
Ca Reactor: Korallin C3002. CO2 bubble rate is about 60 bubbles/min, effluent drip rate is faster than I can count .. 3-5 drop/sec

Ca Reactor effluent: PH = 6.65-6.70, dKH = 35-40

Tank Ca = 450-475
Tank PH = 8.0 - 8.3
Tank dKH = 8.5 - 9.5

The only parameter I'm not happy with is "Tank dKH", which I would like to see in the 10-12 range, but I hesitate to push the Ca Reactor any further. Should I suppliment (something?) to get the Alk up?
I'm not sure how big or new your tank is, but I suspect that there is a lot of bio-activity that's contributing to your carbonate consumption through neutralizing acids. Another unknown is your media; I guess it's possible that different reactor media produce a different balance of calcium and carbonate ions, although I have no experiences or knowledge of this. But, let's assume you're using ARM; it sounds a little low on the dkh end, although Gary is correct, 8.5-9.5 is not a problem as long as it's stable. You might try testing water you're going to use for a water change before you do so; just mix up some water to the SG you use, and test for carbonate hardness. Might be interesting.

Also, I KNOW I read somewhere a very interesting post about the chemistry end of the interaction between calcium reactor effluent and KW. It was more complicated than one would think, and the guy basically was describing some conflicting reactions that would result in carbonate hardness dropping. I never found that post again (reefcentral about a year ago) and I never bothered to ask Randy Holmes-Farley about this idea. I suppose it's worth looking into, if you're loaded with extra time...

You might also just try the easy way out, which would be to SLOWLY add some buffer over a week or so, get your dkh up, and see what happens. Don't be surprised if your Ca drops as a result of this, but it's fine.

Wish I could be more help!

Matt