The fact that the pond only has mudminnows now maybe a clue to the fact that it has a propensity to winter kill... Mudminnows are highly tolerant of low DO while most game fish are not. The fact that there are no game fish present now scares me. 14"-18" of ice for a couple of months will be serious issues for a weedy pond. I would strongly look at renovating the pond and digging a deeper area that exceeds 12' if you wish to have a pond that will see the game fish survive a winter.
