I didn't see what the surface area of the pond is - maybe I missed it. Even if it's little, 1/4 ac or so, and it stays 5 ft deep, I'd say it has a chance of being a good pond, expecially since it survived a bad winter 2 yr ago. You might consider clearing some of the trees away from around the pond and maybe dropping a big one in it, if that's practical. A large oak fell into my small pond during an ice storm a year after I built the pond, and 9 yr later most of the tree is still there and providing shelter for small fish. Your pond may have had too many fish, and a small change in the environment may have tipped the scale against them.
