I got a snowflake and zebra eel for my 300 gallon reef. The zebra is 3.5 feet and snowflake is 3 feet and 2" thick. Big fish. They were model reef inhabitants, but due to their large feeding requirements of 4 jumbo shrimp every 4 days each, I had water quality issues and they knock everything over. Set up a 180 gallon fish only for them. I could not imagine keeping the snowflake in anything less than a 180. I would definitely go with a smaller eel for a 55 gallon or you will be doing water changes like crazy all the time to keep your water ok.
