Any of various small, shrimplike, chiefly marine crustaceans of the order Mysidacea, the females of which carry their eggs in a pouch beneath the thorax. Also called opossum shrimp.
The young Mysids are housed in the ten gallon rearing aquariums at a density of between 1200 and 1300 per tank.
Despite their widespread use as pollution bio-assay organisms, Mysids are not too demanding in terms of water quality (as long as the values remain within a reasonable range).
Some degree of caution may be in order as these butterflyfish attacked the Mysids with such ferocity that their snouts became bruised from repeatedly hitting the tank walls and bottom as they captured the shrimp.