welcome to PB IL....get used to the acronyms \:D

how do you know they are HBG?

are you sure the pond infill is silt and not muck accumulation? if muck, aeration might fix problem, if silt, then digging out is appropriate.

i'll let others here address your fish stocking questions..(i'd have probably dug first and started over.....but that's me).

GSF are people too!