Calcium isn't as important as Alk, so you don't have to dose it a small amount through out the day as you do for Alk. However, if you dose it too much at once, it will precipitate and also clog your pumps (Powerheads, return pumps) really quickly (Same thing happen when you dose slow but your Cal level is too high). Using it in the top off might not be the best idea because someday, the evaporation rate will be higher than other. And also, it will clog your Auto Top Off pump very quickly. If you don't keep SPS and Clams, you don't need to really worry about dosing Cal. Water change will take care of it for you. If you want, you can put a bit of Cal into water change and call it a day. Now if you are going to keep SPS or Clam, then you really need a dosing pump or cal reactor.
