They will eat anything they can get their mouths on, so anything that rests at night- and is not too big for it- it will go after. It's just the way it is with eels. Also, snowflakes are major escape artists. I once sat and watched one leap completely up and out of my acrylic tank- yes, a standard acrylic with the bracing on the sides even! I saw him do it but it still seemed so weird after it happened. Like a living spring or something.

On the bright side, they look really cool. I just love watching them slithering around in the tank. I can't wait until I have enough room/money for a second tank, it's going to be non-reef with some combination of triggers/snowflake eels with a puffer or lion.