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. Reef Advantage strontium contains 30, 000 ppm of ionic strontium. Do not overdose: excess strontium may enhance the loss of carbonate alkalinity. Do not directly mix with any carbonate supplement. Best if strontium & carbonate additives are added on alternate days or at least 30 minutes apart. Guaranteed analysis: strontium (SR) 3.00%