Biological processes, precipitation, and incorporation by marinelife all deplete strontium from aquarium water. Two Little Fishies Strontium Concentrate replenishes it to maintain optimum water quality for growth of corals and other marine organisms that deposit a calcareous skeleton. For aquariums with dense growth of reef building corals, this supplement provides an extra boost of strontium that enhances the deposition of calcareous skeletons. Does not contain molybdenum. 250ml (8.4 fl oz) bottle.