They arent hard. Dont keep them with anything that will ever fit in thier mouths. They don't seem real fond of fast swimmers zippin by them alot, but they deal with it. They like to have ledges to kind of perch on.
What kind of lion are you thinking of and what size tank do you plan to put it in? .. I have a Fuzzy Dwarf Lionfish and he's a great fish .. I have him housed with a Blue Hippo Surgeonfish, 2 Snowflake Moray Eels, 1 Longspine Urchin, 5 Turbo Snails, and 9 Astrea Snails
