My 65 is the same a yours. Its not the same as a 55. its a 75 cut short. Go with a pair of salvinis. There mean got color. And can live for life in the tank.
You guys are right my mistake I was thinking a 60 gallon 48 x 13 x 24. I agree a 36 x 18 x 24 is an odd size tank. I still say angel fish and a couple of small acaras though, def no GT in a tank that small.
Personally, I wouldn't keep any potentially 12" fish in a 36" tank. And before anyone chimes in to point out how few fish actually reach their full size in an aquarium, maybe if people kept their fish in proper sized aquariums, we would see them reach their potential.
I wouldn't keep anything much larger than a Salvini/pair in a 3 footer. And definately not a Midas, Jd or GT, or at least not for anything other than a grow out.