Snow Flake Eel Tank Mates IMO
-Lionfish
-Trigger Fish
-Large Damsels ( Huge Dominos)
- Large Tobys
- Large Big Bodied Gobies
- Puffer Fish
-Groupers
-Batfish
....Pretty much any BIG BODIED FISH....I caps that because you can have a long slender fish be easily swallowed by an eel.
Also another tip, Predetors can and normally do become prey if tankmates are to large....such as a Large Lionfish (Has a large mouth) can devour small eels.
Hope this helps a little...
like the list...personally I would leave out triggers as they tend to "nip." For mixing with snowflakes and other Echidna species, I would also suggest things like large hogfish (Spanish, Mexican, etc), grunts, soldierfish, high hats, things of that nature which are large and fast. Might not work with more aggressive piscivores though