By itself, you need at least a 45, probably a 55 would be better. they are very personable to people and very cool as pets. feed and keep pretty much the same as an oscar, but they are more sensitive to temperature flux, so make sure to use 2 heaters that combined are more than enough wattage for the tank. also keep up on the water changes too. Best to start with a Younger one and a good sized pleco, so that the GT is used to having an algae eater in the tank. yuo might wanna start a smaller tank to breed ramshorn snails, because GT's that i have had love them.
Good Luck!