ca reactor question

[kolosy]

setting one up for the first time, trying to get my head around the settings.

my understanding is that you balance the effluent flow rate with the bubble flow rate to hit a specific pH. but if that's the case, then why do you need a pH controller?

[RokleM]

That statement would be mostly correct. Typically once you get to a point in reefkeeping where a calcium reactor is a full blown requirement, most of those individuals already have a controller of some sort (Apex, AC3, etc). In that case, you already probably have a probe, so it's just a matter of switching an outlet on or off. Even if you don't have a controller (which I'd recommend given the fact many of the heater controllers, pH controllers, etc will end up costing more than a quality full blown reef controller), many buy a pH controller vs monitor as the prices aren't that different.

That being said, you absolutely CAN run a calcium reactor with just a pH monitor instead of controller. If your regulator is solid, little variation, pump pressure and co2 pressure is constant, then it's a matter of getting it fine tuned and letting it run. Most people use a controller as it requires less precision and is a good backup in case something goes wrong.