when i was in college i grew a red to about 11-12" and he absolutely demolished a live mouse (was the coolest feed i've ever seen).
I also put a live mouse in w/ my 6 P's and they were scared for a while (so i did the pull out and reintroduce game a while) and they finally finshed him off.
Besides that the best feed i had was a 8" gold fish feeder i fed to my 6 P's and they literally finished it off in about 10 seconds all attacking it!