In neither case (Big BG or Big LMB)would I remove my biggest male and female BG. Those BG are the ones who will reproduce the most BG fry and see them to swim up stage. In a big BG pond I would remove more medium sized BG while in a big LMB pond I would not remove many BG at all. If I wanted big LMB then remove lots of smaller LMB if you want big BG don't remove to many small LMB. I agree with Bill on the pond size matters he discussed.