Rusto,
You are going on 3 years and so I'd think its not too early (in the life of your pond) to add some crays that are well adapted to living in ponds and lakes. Northern crayfish (Orconectes virilis) in your locale. If you can obtain adults right now, the females will produce between 250 and 400 offspring as the temp warms up. With all that FA, the cover should allow enough of them survive to produce a crop of young crays. Their activity could provide some control once the younglings leave the moms. The additional forage for your LMB and BG will more than compensate their initial cost. This is preferable over adding copper (is toxic) which will accumulate in your ponds sediments. By the time your TP are reproducing the craws will have provided some control and the action of the TP offspring on the FA will expose the remainder of the crayfish to predators.
If you know of small pond without fish nearby, you can trap local open water crays and move them to your pond in larger numbers. The dominant cray in these environments in your area will likely be the Water Nymph crayfish (Orconectes nais). It will work too but isn't as hardy against fish as are the Northerns. With a strong predator fish population, you may have to strengthen the population each year, so a local source where you can seine or trap adults and offspring would be a big help.
