Let me give an alternative explanation for what you observed when you scrubbed out CO2 and found the alk to decline. That can and will happen because both coral/coralline uptake of calcium and alkalinity and abiotic precipitation of calcium carbonate rises as the pH rises.
Well, I'm sure what you describe does happen, but perhaps not in my case. The first part, definitely not - This was a relatively acute drop in alk, over about 4 days while I was running that scrubber, and the tank was not that heavily stocked at the time, and mostly new-ish livestock at that. The alk drop was not biotic. Abiotic precipitation - This is always the answer that people give for otherwise unexplained alk drops, because it's hard to disprove, but I witnessed none in my sump, which is where I add two-part, nor did I see any on the glass in front of the return, where I'd also expect it. As I said though, hard to entirely disprove; could adhere to the gravel and you'd never see it.
I'm confused more now than I was.
LOL! Brother, I know how you feel. I haven't yet read the articles that Randy references regarding this business, but I intend to.
And after all this, I still think it's still ok to dose different amounts of two part (as long as they aren't
too different), if that's what it takes to keep your tank in the happy zone. I keep my calcium at 430-450 and my alk at 9.5 by dosing about 11% less Reef Fusion 1 than Reef Fusion 2. I am running low but not ultra-low nutrients, so I feel that these numbers work for me. My corals seem to like it too. Equal amounts simply did not result in the right ionic balance, and although I struggled with the decision, I do not regret 'unlinking' the dosing. (Although I'm finding that the magnesium in RF1 is just not enough, especially as some of the monti's start to take off, but unlike another forum member, I'm finding low Mg very easy and safe to treat with liquid Magnesion. Maybe he forgot to shake it first? You definitely need to shake that stuff. )
