Found these answers, on another forum which shall not be named:
"I'd be careful with corals as well. As the snowflake gets bigger, he could knock down some of your rockwork which may include your corals. Eels are very strong fish."
"The above post is correct, eels will east shrimp and crabs. The list of tanksmates for a snowflake eel is long. No clownfish, no damsels, no cardinals, no gobies and nothing else too small. Also, no groupers as they may look to eat the eel. But you can go with tangs, large angels, rabbitfish, triggers, butterfly, anthias, squirrelfish, etc...."
Looks like there are a lot of conditions for this particular eel. I love FW
eels, but admit I do not know about saltwater eels. What I do know is there can be variations in eel personalities and aggression, in my experience. The striped one I have now is pretty lazy and won't outright go after fish to kill them. The senegal I had before this one was a killer, and ate everything including his identical tank mate.
It's a shame they can't be more communal, and the snowflake eel is just stunning. Maybe you could set up a tank just for one.