There's plenty of good ol' info on the Interweb....Crappie are Great for Aquaponics...most everyone I know use Tilapia, because they can be packed together, grow faster than other fish, and are vegetarian!

Don't add Bass, Crappie will eat their own, you will eat the larger fish...if this is an outdoor system, you can use Lowell's free food system....hang a platform over the tank, put rotten meat, roadkill, etc, on the platform....flies will come, then maggots will fall into the water feeding the crappie also!