Lets see what Bill and some of the other experts have to say, but I don't think that the YP and WE will be able to keep up with the rate of BG reproduction. The other part of the equasion is that the YP and WE normally occupy a different part of the pond's water column than BG, so will have to travel further to get a meal. I think that the WE will tend to target more YP than BG for meals.
That's my $0.02 worth!
Heck no, don't fill it in. That pond is part of your Dad's legacy.