I'm staying faraway from the ethics of keeping Pomoxis nigromaculatus in a 10 gallon tank, but as far as feeding it goes, I can answer that for you.
Spend some time catching natural food for it, or any wild fish you keep. It will not be used to eating goldfish flakes or pieces of bread. Their natural food will be much healthier for them. You can try shad, minnows, shiners. Some kind of zooplankton, insects, and crustaceans will work also.
Edit:
But in all honestly, you may as well gut it, fillet it out and fry it up... because all you're going to do is kill it in that size of aquarium.