API Marine Complete Trace water treatment acts as an all-natural source of over 60 trace elements found in seawater, plus iodine. It replenishes trace element imbalance in marine and reef aquariums caused by protein skimming, as well as other natural aquarium processes. API Marine Complete Trace maintains proper water conditions in aquariums containing hard and soft corals, live rock, coralline algae, crustaceans, starfish, and saltwater fish.