There's alot more to tank size than the size of the fish. These are aggressive eels that have rows of sharp fang style teeth that rip and tear apart fish, fish are their main diet. They are strong dynamic swimmers that will get as thick as a man's forearm. Please don't listen to someone that has a baby banana eel that they have had for a couple of months, and tell you that they are a model citizen. And sadly most never keep snowflakes to maturity and they deserve a larger tank than most provide. If you were to keep the banana eel alone in a 90g or with another comparable eel that would be fine. But for any fish to survive, a 180g would be the smallest tank appropriate, the fish would be the size and aggression to need at least a 180g.
