A regular goldfish?
See my sig they are all together in one. Goldfish can handle up to 75 and fancy can handle a little more. The warmer the water, the more they poop and more oxygen they need. I am still tunning my temp and its at 78-79right now (aiming for 76-76.5), waters well aerated so they are fine. 77 I would say is the max temp.
none of the tropical fish in your sig should be kept in a 3ft tank, which is what the OP has. compatibility problems aside, they all get too big.