They main threat they would pose to corals and such are high nitrates, being carnivores they will and and process alot
they should be OK with snails and small hermits but bigger one and shrimp may become snacks. Also they will like lower light than so an
SPS tank so a simple softy ie
star polyps, shrooms, ect tank with ledges and rockwork for hiding should be OK
They can eat anything they can fit in mouth , up to nearly there own size, so companians must be chosen carefully. Last but not least , removing one from a reef tank would be a chore if its stubborn, also remember not to pet them
