once i get my MH im goin to buy three clams and a lot of other coral
Once all this is in place yes, you may need one. Of course, i'm assuming "corals" are the stoney types.
Won't a calcium reactor only add calcium and don't they do best in tandem with a Kalk reactor for pH stabilization?
No and yes. It will add cal, alk and trace elements. It's basicly dead coral in the media. Dead coral once lived (duh) and of course took all it needed from the ocean. Your just disolving it back into the water colume.
But, it does lower the PH. The kalk will counter act that by raising back up.
Or you may do the drip method.
BTW my cal went from 250-300 to 400 by using crushed oyster shells in a large filter box.
The last I read, this wasn't proven. It was just about dis-proven. I guess time will tell.