Two Little Fishies Iron Concentrate is a solution that contains the elements iron and manganese, which are essential to the health of all plants, including the symbiotic zooxanthellae in corals and sea anemones, and sea-grasses. Two Little Fishies Iron Concentrate safely replenishes iron and manganese in the proper ratio, which helps maintain optimum water quality for the growth of corals and the macro algae that are commonly cultivated in refugium aquariums. 250 ml (8.4 oz) and 500 ml (16.8 fl oz) bottles