Kent Marine Kalkwasser Mix will provide supplemental calcium to reef inhabitants such as corals, snails, hard tube worms and clams as well as allowing for lush growth of purple, pink and green calcareous algaes. Kalkwasser is the original European method of adding calcium to a reef aquarium. It is a unique system that allows corals to lay down new layers of calcium carbonate. This application is a bit more work, but provides positive long term results. Shipping weight: 3/4 lb.