Yeah. I think it really was just a matter of overgrown fins, as there's only about a quarter of his caudal fin left, even though I've tried more plants, different plants, different arrangement of the plants, a larger tank, a better heater, higher ratio of his favorite food to pellets, and changing location of the tank. He seems pretty hell-bent on eating as much of his tail as he can.
Reminds me and my girlfriend of the Goldfish crackers song: "I got fishes and they're so delicious..."
..that they eat themselves.