There are a number of different species of shrimp sold as "ghost shrimp". All are collected in the wild, and it isn't unusual for more than one species to be caught together. Occaisonally juvenile prawns (longarm shrimp) are mixed in, they look quite similar to other species when small. One species, Macrobrachium rosenbergii, will eat other shrimp, and eventually fish as well, if it survives in the aquarium. M. rosenbergii grows to nearly 12".