Catfish can thrive in ponds of different depths, depending on their variety and the regional weather patterns. Channel cats, of course, are the most popular species, and they do require some special conditions in order to thrive. If you live in an area where ice covers your pond during the winter, the pond needs to be deep enough to permit them room to move around beneath it. A good rule of thumb is to allow at least 3-4’ of clear water below your average depth of ice. If you’re in a colder US climate zone, your channel cats can probably do fine at 6’-8. You’ll hear different numbers from southern agricultural extension agencies, where a pond depth of 5’ is considered acceptable. Most professionals recommend a steeply sloping (or dropoff) edge that goes quickly to 2’ deep then slopes down to the maximum depth. The strategy here is to discourage growth of aquatic weeds that can quickly overtake your pond.
Contrary to popular belief, very deep ponds are actually not well suited to farming catfish. Deep ponds can develop stratification, with associated temperature and oxygenation differences. Detritus at the bottom of the pond is not easily managed, and low oxygenation can lead to the growth of anaerobic bacteria, which release toxins into the water. You can mitigate this risk by making sure you’ve removed dead trees and other bits of detritus from the pond bottom and clearing it out from time to time. While these natural structures provide attractive spawning locations, if you plan to continue stocking your pond, locally spawned fry can disrupt the balance of your pond and lead to poor growth for the entire population.