I had an SnowFlake Eel in my 33 gallon for more than 2 year.
It was OK, it had enough space, she didnt noticeably grown in 2 year, the bioload was ok (It wasnt a big deal).
BUT: I would NEVER suggest you an eel! Mine was SOOOOO agressive with fish and with my finger!!!! she eated my clown fish after 1 month! She snaped my finger while I was working in the tank like 3 times!!
So finally I gaved it back to the LFS
since it was WAYYY to much agressive for my tank! Its like impossible to have anything else alive in the tank when having one of them!!