FHM, due to their slow swimming speed, and the male nest guarding habits, are easy pickings unless there is ample cover/habitat for them that excludes predators - a "safe haven" so to speak. Without ample prey fish specific habitat, I think they will be easy pickings in a pond and won't last more than a few years. Especially if they are the only forage fish.
GSH are broadcast spawners, lay and forget. FHM, even the largest specimens can be eaten by large YP. I was catching YP last Spring on 4" and 5" minnow imitation jerk baits.