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. The first and only 10 minute strontium test! The test involves separation of strontium from the sample by a highly selective extraction technique, followed by a sensitive titration in 0.5 mg/L increments. The sample is treated and filtered through an adsorbent to selectively remove the strontium from solution. The filtrate is discarded and the adsorbent is washed to remove residual sample. The strontium is then eluted from the adsorbent and measured.