Sunil, I will look into the Shiners. Can it be done incrementally by year or will they get decimated in low numbers? I think the alkalinity was 270 when I first stocked it. Don't remember the ph. Tested with a pool kit. Are there any kits specifically for testing ponds?
In short, yes, you can do it over time. The overall impact on the predator fish population would be lessened, but still, there would be benefits.
Any kind of structure you can add that would help survival of the shiners would be good. Brush piles, Christmas trees, etc.