[Delphinus]

My own take on reactors and kalk has me doing a little bit of both.

I personally find the constancy of a reactor to be its biggest selling point. The Ca and Alk levels are closer to constant, rather than a sudden addition and slow depletion on a daily cycle that I was getting when I did two-part additives. I find the corals do better too, despite that the levels aren't always as "good" as what they were when I was doing the two-parts. I truly believe the fact that the levels are constant, i.e., being replaced as fast as they are consumed, on an instantaneous level as opposed to a once-per-day kind of thing, contributes greatly to that.

And, it's great that I don't have to train someone up to do my additions when I go away for a couple of days .. the reactor will stay on the job.

That said, now, I do dose kalk in my topup. Primarily for pH control. I find with the kalk, my pH goes from 8.2 to 8.4 on it's daily swing, and when I stop the pH swing goes to 8.1 to 8.3. Is 0.1 difference worth the effort? I'm not sure. But when I first started dosing kalk after switching to a reactor, my pH was more like 7.9 to 8.2 and that caused different problems (valonia, dinos, hair algae, cyano). So the kalk did definitely help the tank settle in after the reactor. I don't have a refugium on reverse-daylight-photoperiod so I don't have that as a crutch for pH control.

On my other tank (my ritteri tank) I just dose kalk, and it's not near enough to maintain levels for SPS. Luckily, that's not the goal for that tank, so it's not an issue for me, but I thought I'd mention it since it supports Jonathan's and Doug's observations/thoughts on the issue. There are a few small pieces of SPS in that tank, and they grow much slower because the alk/Ca are more like "moderate" as opposed to "ideal." I should also point out that I have had two incidents of SPS bleaching in the last two months on this tank, because the kalk did something screwy (I once found my pH as high as 8.6). Most things tolerated it except my purple montipora digitata. Not sure why the kalk did that because it wasn't a case of it got added too quickly. The corals recovered in a day or two but this DOES illustrate, in my opinion, that kalk is not a risk-free approach to maintaining levels.

Reactors are the only way to go.

cheers