I'd say the catfish is certainly a predator.
I had a catfish my pulled out of the local river that I kept in my freshwater aquarium when I was in college. I bought 100 feeder goldfish for it and the catfish wouldn't eat them. On the third night, I turned off all of the lights in my apartment, including the tank light.
About five minutes later, as I was trying to fall asleep, I started hearing someone walking around my apartment, or at least knocking on the walls. I turned on my light and the sound stopped. When I turned the light off, the sound started back up. This happened once or twice more before I grabbed my flashlight and looked around the apartment.
I followed the sound to the fish tank, where the catfish was patrolling with his mouth hanging open lazily, just inhaling goldfish from one end of the tank to the other, where he would bump into the glass, turn around, and continue his path just like he was mowing a lawn.
By morning I only had about thirty goldfish left and the catfish didn't eat for another four days. After that, I figured out that I could keep the lights in the rest of the house low enough to watch him feed and he put on many shows for visitors. I left for Alaska that summer and had to give him to a friend who got tired of feeding him and released him back to the lake where he had come from.