A useful emergency way to raise DO levels in a pond is to mount a small outboard engine in a fixed position, e.g. pier or boat that is unmovable and run it wide open for a while. I haven't had to resort to this, but know of commercial growers who say that in a power emergency coupled with DO crash, that is what they do....effectiveness is limited by the ponds size, i.e. a very large pond wouldn't benefit much from this but it seems like a small one would, in an emergency.
