I do not have a calcium reactor but have been looking into them as well for the last month or 2. The first thing you need to determine is your calcium and alk demands because you may be able to keep up using only kalkwasser. There are many in the hobby that do this to help maintain pH as well. A new calcium reactor setup will easily run you 500+ by the time you buy the reactor for 200, regulator for 200 and then a co2 tank and solenoid for 100+, you will then need a pH controller of some kind to regulate the co2. That could be a $50 probe off an apex/reefkeeper or a 150 milwaukee controller for only pH. If you watch the forums you may be able to score a whole setup for 200-400...