Reef advantage strontiumr reef advantage strontium restores and maintains strontium to levels found naturally in sea water strontium is utilized by corals in much the same way as calcium and holds a similar importance in maintaining vigorous levels of growthreef advantage strontium contains 30 000 ppm of ionic strontiumr directionsr 300g treats 2400 gallonsr use 8g 1 level tea spoon per 150 litre 40 gallons twice a week