I personally wouldn't keep them in anything smaller than a 100 gallon. Snowflakes get around 24" and can get thick. I have two of them in a 240 gallon that are around 18" or so and when they come out to swim they move quick. Also make sure your rocks are stable because they will burrow and make tunnels and knock over stuff. Make sure you have a secure fitting top with no holes because they will find them and probally go carpet surfing. As for eating fish, one of mine attacked a Picasso trigger that was about 3". The trigger was in a cave and i saw the eel sneak up on it and grab it, it let it go but it didn't survive.