Reef Advantage Strontium, 4 kg / 8.8 lbs Raises strontium in reef aquarium Restores and maintains strontium levels found in natural sea water Strontium is utilized in corals in the same manner as calcium and holds a similar importance in maintaining a vigorous level of growth Contains 30,000 parts per million of ionic strontium 300 grams treats 2400 US gallons