Baby crayfish, minnows, cichlid pellets, worms, pretty much anything they can catch and fit in their mouth. They're a type of cichlid if I remember correctly. Where I live there is this boat ramp that's on this really shallow stretch of creek, and you can see the adults guarding their eggs, they make these nests out of pebbles (you can pretty much spot them because they seem to be a slightly different color than the surrounding rocks) and chase anything that gets near. And yeah, they are very personable fish, which is probably why I found a lot of tropicals disappointing when I got them, I was spoiled already...
You can find small babies in the spring, they hide out in rocky parts of the shore in the river, you can catch them with a regular tank net if you're quick, just make sure you don't catch any bass unless you want them too (rock bass are awesome!). If you are looking for them in a creek take a minnow sene (can't spell lol) and take a partner, it helps a lot. Then you can not only get a pumpkin but chubs, minnows, and a few other things, which can go in the tank too (don't try with red daces though as they die pretty easy, and throw any really big fat minnows (minnows, not chubs) back because they're eggladen, and it's better to keep them in the wild.
Oh, and watch out for pissed off water snakes and copperheads! They look a lot like water snakes until you get close, and you really don't want to get to close lol.
Tell me how it goes!