Two Little Fishies' CombiSan is a bio-activator that contains all essential trace elements in special compounds easily absorbed by invertebrates, micro-organisms, and marine fish. You can depend on CombiSan to replenish deficiencies in the composition of aquarium water resulting from protein skimming, use of activated carbon, biological processes, precipitation, and extraction from the water by marine life. CombiSan fosters the development of pink calcareous algae and the rapid growth of reef building stony corals. It promotes tissue repair in fish, and brilliant coloration in photosynthetic corals, anemones, and Tridacnid spp. clams. It's the one marine supplement that does it all. CombiSan is nitrate and phosphate free! For optimal results use CombiSan and Two Little Fishies Kalkwasser, the formula Wilkens developed over 20 years ago to replenish calcium and maintain alkalinity, benefiting corals, clams, and calcareous algae that build skeletons, shells, and crusts from calcium carbonate.