Whether or not the bullheads and channel cats were the cause of your muddy water would depend on several factors such as size/depth/detail of the body of water, and the density of catfish.
If you don't care to fish for them or have them as a fish, I don't think there's any reason to stock them. They don't really serve any other purpose except being a mouth(s) to feed, or another type of fish to catch. In some ponds or lakes they may be an important part of the predator-prey relationship.
Shorty, I don't think you're saying to stock some channel cat just to create some less clear water, are you?
