Your pond is too small for crappie. I would remove all I could; along with green sunfish and bullheads. You have enough bass. A pond can usually only accomodate 100 pounds (or less) of predators like bass and catfish per acre. Your bluegill will be the future key to success. After a couple of years start keeping all LMB under 12 to 13 inches.

I would also subscribe to Pond Boss magazine and buy the book "Raising Trophy Bass" by Bob Lusk.