Just my opinion, but I don't think a pond can be too small for catfish. They are very resilient, plus being fun to catch and eat.
I certainly agree with all that has been posted above with our good friends ESSHUP and CJBS.
Our property in northern West Virginia has several ponds, and I help manage other ponds in WV and VA.
As I've posted a number of times in other threads, I have a love/hate relationship with channel cats. They are very inexpensive to stock. They take food readily, and they grow really fast. As a food fish, they are great at all sizes, but especially from about 14 inches and up. Each several inches makes them more delicious and more versatile for dinner. A 20-inch catfish, or larger, can easily substitute for any number of great saltwater fish recipes.
In the middle, there is a point when they are still easy to catch, and a lot of fun. But, they aren't quite big enough for a good catfish dinner. The kids will love this era.
Channel catfish at all sizes will add turbidity to your water as they scour the bottom of your pond for food. That is not all bad for a number of reasons. It will cut down on weeds and algae in your pond. They will stir up the muck in the bottom of your pond, making it decay faster.
If you have an older pond, you can usually determine exactly where they are. Lots of small bubbles come to the surface when they are digging for forage.
My most recent favorite way to catch them is with big creek chubs (6-8 inches, strung with 6/0 circle hooks in the tail and lips). I catch the creek chubs using hook and line, with small redworms on a #8 hook a the end of a fly line leader.
To catch the catfish, I "freeline" the minnows at dusk and beyond. That is, I hook them through the lips, and through the tail. No bobbers. No weights. Nothing else. The hooked minnows get thrown out into 4-5 feet of water.
The same thing can be done with shrimp that has passed its "sell-by" date at the supermarket. I'll take a handful of these shrimp, cut them into small pieces, and throw them where I think the catfish will congregate at dark. Then I put in one to three lines with more shrimp, each with a #4 or #6 circle hook.
In either case, I almost always come out with what would be a trophy catfish to most people.
Fileted, skinned, and blackened, broiled, or fried -- life is good.
Put some in your pond -- just not too many.
