A green moray for 12 years in a 220? That is outrageous, IMO.
Healthy green morays are huge animals and I can't even imagine one in a tank that "small."
Please do not get one unless you can keep it long term, and yes I agree you need a very very large tank.
DO NOT ASSUME A PUBLIC AQUARIUM WILL TAKE A GREEN MORAY. Most have more than they could possibly need already. There are plenty of eels suitable for "smaller" hobbyists tanks.