I feed mine 3 times a day usually and he is kinda plump. lol When I got him you could see his spine bone he was awful thin. Not sure on the life span, I;ve had mine since I got my cube, which was maybe 2-3 months ago? He has also grown about triple his size in that time.
He is an awesome fish, his tail is really red and when he flips up his sailfin thing it's beyond cool.
Just can't recommend one after all the trouble I've had.