Observation of amazing fish behavior

[Ilsa]

I have a fresh water thirty gallon tank. One of my red platys appeared to have gotten stuck on the filter, so I shut it off. It took about a minute for the fish to be able to release itself, which I don't understand since it doesn't appear to have any external injuries.

Anyway, the fish couldn't swim with its tail fin, but it managed to settle against a rock at the bottom of the tank. Another red platy came over to it, and has been trying to stimulate it by rapidly flipping its tail fin around it. It is amazing, because that kind of activity is normally used to propel the fish rapidly forward. The second fish has stayed close to the first one and periodlically tries to "beat" to help it move. These fish seem to care about each other!

If anyone has had this experience and knows what is going on, please let me know. The injured platy can't seem to beat its tail fin and its attitude goes vertical when it tries to swim.