I have always ever used CoraLife for my main and octopus tank. No problems whatsoever. In fact when I recently purchased a Salifert Calcium test kit and tested a new batch, came up with about 450 Calcium in the fresh batch of saltwater, not bad!
P.S. My new seahorse seems to be doing fine in it as well - healthy, slowly moving around the tank looking for copepods, and eating the first night I brought him home...