Without a doubt, the easiest product on the market for dosing calcium and trace elements. A great product for beginning and advanced reef keepers. Simply drop in several cubes and wait for them to dissolve. Once dissolved drop in the next batch. Impossible to overdose- the nuggets dissolve only to replace depleted elements. As elements are depleted from the aquarium, Formula 28 delivers exactly equivalent amounts to replace them. Sea Lab 28 is a mixture of naturally occurring buffer compounds that maintains natural concentrations of calcium, strontium, and 15 other essential trace elements.