I personally think a 55 is too small for a male gt.... a male will reach 10" if not bigger and will get really thick.... I have a 8" male and i could not imagine him in a 55.... sure a GT can live in a 55 for a while but since your not upgrading I would suggest you look into other cichlids such as salvini and other small cichlids....
its not the length of the tank its the width gt's get 12" long and the tank is only 12" wide.... making it tooo small of a tank.....4 feet> 8 inches. Sounds fine to me
If you would do your research you would know gt's get too big for a 55....just get the GT if u want it, a 55 is plenty big enough for one. However he might not tolerate other fish in his space. i have a male GT about 7" in a 75 and he gets along fine with many bichirs, loaches, and the FL Gar but wont tolerate anything that looks like a cichlid.
its not the length of the tank its the width gt's get 12" long and the tank is only 12" wide.... making it tooo small of a tank.....
If you would do your research you would know gt's get too big for a 55....