Dwarf Octopus - TBS farmOctopus mercatoris are unique predators that require a species specific or FOWLR system. Dwarf octopus prefer eating crabs and shrimp. Have a mantis that you can't trap? Well, the dwarf octopus will catch it and clear out hermit crabs, pistol shrimp, peppermint shrimps, and gorilla crabs, too. They are nocturnal, so don't plan on seeing it under bright lights. Mercatoris are shorted lived, up to 2 years.