Strontium occurs in natural seawater at a concentration of about 8 to 10 mg/L. It is chemically very similar to calcium, and many organisms incorporate it in their skeletons along with calcium. Its addition to reef aquariums aids the growth of corals, coralline algae and other organisms that lay down a calcereous skeleton or shell, including tridacnid clams. Reef Advantage Strontium™ restores and maintains strontium to levels found in natural sea water. Strontium is utilized by corals in the same manner as calcium and holds a similar importance in maintaining a vigorous level of growth. It is most useful in densely populated aquariums requiring a continuous supply of strontium. Reef Advantage Strontium™ is a highly concentrated (30,000 ppm), ionically balanced strontium supplement. Unlike other strontium chloride products, Reef Advantage Strontium™ is formulated so that it can be added directly to the aquarium. Competing products require one to mix a separate solution before adding it to the system.