I agree with Duane on this. Don't put an 8 - 10" fish in a tank that is 13" wide. While there may be enough physical space, it'd be like you never leaving a studio apartment. The large fish I've seen in 55s either sit listlessly in one place or they nervously pace up and down the tank. I use 55 for growouts or for breeding tanks for small to medium cichlids, up to the 5 - 6" range. And even at 6" that's pushing it because if a male turns on a mate, there's nowhere to really escape.
A 75 gives you a good bit of extra width. For a single wet pet I'd go no smaller than that.