I'm not sure what species a redtail catfish is, but if it's a member of the North America catfish family, it's a scavenger, meaning that it only eats other critters, dead or alive. Food includes insects, worms, fish; any animal or animal part (slow-moving or no-moving) that smells good, fits in its mouth, and can't swim away. Catfish might dislodge plants in muck while they're searching for food, but they don't deliberately uproot them or eat them.