anything that can fit brine shrimp in it's mouth will eat them. As newly hatched brine shrimp is what is used for a lot of newborn fry, just about any fish will eat them.
well i dunno if sea monkeys are saltwater but could be but in freshwater they could be daphnia i had a couple of them in my 10gal when i was raising betta fry they just appeared out of nowhere one day but they were gone after the frys got bigger