The Seachem Reef Status Strontium Test Kit measures strontium by first seperating the strontium in the sample by a chemical precipitation and filtration, followed by a sensitive titration in 0.5 mg/L increments. Now uses an easier to read non-fluorescent indicator!
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.