Your collective enthusiasm is great!
So far I've learned from reading on this forum that Gussy is not a "she" as I was originally informed by it's previous owner; as the lump on the forehead indicates it's male.
The information given to me Gussy is about 10-15 years old, I understand GG's live to be about 20-25 years old. I have seen little to no growth from the fish in the last year that I've had him, would that indicate that he's done growing, or that the tank is too small, or something else? Although Gussy seems to be fine with other fish I've had in the tank (Goldfish, Chinese Alge Eaters) here and there, he did seem to be somewhat interested in eating the crawdad that was residing in the tank for about a week. Otherwise he only eats fruits and vegetables, having zero interest in meat, though the previous owner said he'd happily eat dry cat food.
The last owner was into her 80's, and felt that she could no longer take care of Gussy. While my wife is less than enthusiastic about having "one big, ugly, mean fish" instead of 25 little pretty fish in a tank, she leaves the aquarium stuff to me. I know that at some point in time I'll need to come up with a bigger tank, maybe I can polish the 75 gallon up for her to put little cutsie fish into (Gussy has really scratched the plexi up with his "kissing").
Thanks for the replies and encouragement.