Provides calcium needed for proper growth and health of corals and other reef invertebrates. Restores calcium essential for healthier, more colorful corals and reef invertebrates including snails, shrimp, crabs, clams, mollusks, as well as coralline algae. Use whenever testing shows a calcium level below 400 ppm (mg/L). Provides calcium needed for proper growth and health of corals and other reef invertebrates. Restores calcium essential for healthier, more colorful corals and reef invertebrates including snails, shrimp, crabs, clams, mollusks, as well as coralline algae. Use whenever testing shows a calcium level below 400 ppm (mg/L).