Calcium, Magnesium, & Strontium Supplement for all Marine Fish & Reef Aquaria Overview Contains calcium, strontium, and magnesium in the same ionic ratios found in aragonite. This unique feature increases the usefulness of Kalk+2 to reef-building invertebrates such as corals, clams, calcareous algae, etc. Provides temporary alkalinity and helps maintain pH within the desired range when used as directed. Adds no conservative elements, such as chloride, to the aquarium. Improves upon the industry-standard powdered calcium supplement over the past three decades. Formulated by a marine scientist.