THere are some species of "bluegill sunfish" that are smaller at adult size. One such fish that I keep is called a "Pumpkinseed" (my avitar is a pic of my Pumpkinseed)
A 29 might be OK if you start with a small specimen. Feeding is easy, they will accept most food from the lfs, plus worms, crikets, plus homemade beef heart based fish food recipes.
They are agressive, and even in a much larger tank, you need to have either 1, or 3-5, never just two. One will become dominant and will literally pester the other to death.