Co2 BB gun or rifle.
I also watched the video and I don't really think the occasional fountain had any effect on the heron other than keeping your fish down which gave the heron no target to catch this time.
You could also use hobby rocket solar ignighters, pvc pipe and gun powder. Make a pipe bomb more for noise than anything and hook up a motion senor to it. Played with this stuff as a kid. The pvc pipe is not much of a problem since it don't restrict as much as regular metal pipe, therefore causes more noise than harm.