If it grows on a vine, limb, or out of the ground, Gussy eats it. His preference seems to be fruits like strawberries, blueberries, and honeydew melon.
He's shown no interest in meat, no interest in other fish, and some interest (curiosity?) in the crayfish that was in there with him for about a week.
I've never tried worms, though Gussy's last owner said he'd eat dry cat food....