Gypsum works real well if you can stop the clay from coming in. Otherwise I have found that a suspended clay tank (pond) with a feeder is perfect for catfish. Never a problem with weeds or other fish getting in, and the water is always 10 degrees cooler than clear or just green water. I put in fatheads with the cats but do not know how well they survived. I add about 10 lbs. of fatheads each year. I feed floating feed with one spincast feeder. Four years now and have channel cats to 9 lbs. Only feed from March to end of Nov. here in S. Texas. One feeder 150 lb. each 4 weeks. Tank is approx. 2 acres and solid suspended clay. Tried 2 tons of Gypsum which cleared another tank just a bit smaller, but it did not phase this one. I know Gypsum will work but it would be too costly to stop the clay coming in and I would worry about tank water then. If you like channel cats you have a winner.