Hi Cluster,
I feed my two GSPs that are just under 2", bloodworm and cockle. They love live food as well. With live food, you should pour it into a net (in a bathroom sink of course ) and put some water through it. The take it to your tank and put it in, no need to worry about taking it out.
With frozen delights (such as bloodworm and cockle) you should get the ones in pack from your lfs, the ones with them in small rectangles. Cut the rectangle in half, and cut the remainder in half again. Feed every other day.
I do this with my puffers, and they are very healthy fish. I know I have two, but they are a lot smaller than yours. I read a GSP feeding chart on another forums somewhere. Try typing into Google something like: How Much Should I Feed My Puffers, or something like that, I'm sure it's a forums.