hw-Marinemix Reefer - Calcium 445-450 ppm, Alk 9.0 dKH, Magnesium 1380 ppm is my favorite, Redsea Coral Pro second place. I use Redsea in smaller tanks ( Redsea 130D) and the levels stay stable through WCs. However hw-Marinemix Reefer took first spot for me because it left no residue when mixing, downside is it cost more, but I have been happy with both brands. Depending the the size of your tanks there may not be away to get around dosing, large reef tanks will use elements faster than what a modest WC can provide.