snub, I can support your observation of fish using fin movement. I have only watched CC and noticed a couple times of this. When building a prototype FISharvester I used sheet metal for the floor. CC would swim around outside and make splashes with tails that would knock the feed out of the feeder. When I used floating feed they could also use this same method. I have fixed this by using only sinking pellets and found a PVC panel that is ribbed and has texture to it. Once they realize they can't control the feed they become conditioned to going in and getting the feed. Sometimes it's hard to believe that I'm dealing with dumb animals.
