Here's another opinion...an 8' hole to raise fatheads won't raise enough to make any difference for your larger pond. Besides,fatheads into an established fishery are only a "snack", not any significant source of long term forage fish. Limited value for valuable time and effort, and money. Money may be better spent buying fish food and feeding existing forage fish a supplemental diet.

Teach a man to grow fish...
He can teach to catch fish...