Yes, catfish are bottom feeders. They will, on occasion, gather and eat food from the top of the water, but mainly stay in mid to bottom levels of their habitat where it's cooler. If you have your own pond stocked with them, they can become accustomed to eating from the top if you throw out feed into the water. This is generally a bad idea though as it is not natural of them and animals develop laziness much like humans. Once they become accustomed to being fed from the top, they no longer search on the bottom.