Uncle, I was in your area last fall visiting a friend in Wanooski. Given the relatively small size of your pond, and how you said it is "easily drained", in my opinion, a complete kill off would be your best, and least expensive option. Properly applying Hydrated Lime is not only effective, it is short lived on the pH increase and leaves behind calcium.
As F&C suggested, keeping some current forage and predators to restock after cleansing the pond of unwanted fish should not be all that difficult. You could make a small, sterilized pond within your pond for that
