Calcium Reactor or B-Ionic Additive?

[casademurphy]

I'm looking at moving away from the B-Ionic additives and thinking about purchasing a Calcium Reactor.

Here's the thing, I'm not well versed on what you need when you get a calcium reactor, so any help would be greatly appreciated.

How much would a typical setup cost?

I have a 90 gallon reef tank, so I would probably need something that would fit under the tank.