For raising fat BG, I use a high protein feed(45%) made and sold by Rangen. Purina Game Fish Chow is a good general purpose fish food with about 32% protein.
As long as you get quality fish food at around the 32% protein level, those BG will really take off. Don't make the mistake of using dog food or other food not formulated for fish. You may save a couple of bucks, but your fish will suffer less growth.
p.s. terrific planned use of the pond! My compliments to you.
p.s.s. BG will spawn in just about anything, in my experience. Some folks use gravel beds to help increase spwaning, but I personally have never seen a need for that in my area. Around here, they make the nests everywhere and spawn profusely without any help from me.
