Read an article in a fish-keeping magazine about a facility that had some tanks and their efforts to maintain them during a power outage.
One method was to rig a redumentary two-prop attachment on a rod, which was then chucked into a battery powered hand drill, and the water aggitated periodically.
Another was to put a hose into the tank with the other end hooked to a manual tire pump, although this proved to wear out the pumpers pretty quick.
They did something else involving a bicycle on a stand allowing it to be peddled stationarily, but I don't remember the particulars.