about 24 years ago I set up a 150g tank (6x2x 20") that was to be my reef tank. While it was cycling, an unidentified Eel came in on fish day at the LFS I worked at. It was (at ~20") bigger than they wanted in any of their tanks, so it was given to me. Conventional wisdom of the time said that a marine fish living more than a year or two was uncommon, so I figured, what the hell.
Hannibal is now ~ 48" long, weighs in at ~ 15lbs, and, being a Gymnothorax Undulatus (Undulated Moray) one of the meanest critters in the ocean. He has eaten everything I have tried to put in with him (hence the name). Oh - and it turns out his lifespan is somewhere in the 30 to 50 year range.
Guess that reef will have to wait.