RAH,
That is a nice little pond that you have created. Have you considered draining and starting over?
You might be able to pick a time to drain this summer when it would have minimal impact on all of the wildlife utilizing that pond. You could then re-start the pond with the ecology of your choice. You might only get 2-3 years before the next high-water event that puts GSF into the pond, but you could have established PK and a few larger LMB by then that could have a chance of extirpating a few invasive GSF.
