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It's difficult to see, but there are some signs that indicate it a Stratiomys species. around 39-40 seconds of the movie you can see small white spots on the dorsal side, which are absent or hardly developed in Odontomyia. The shape is definitely not S. singularior (longer terminal segment) and the habitat and location seems peculariar for S. longicornis. I cannot rule out Od. ornata entirely, but your specimen may in fact be something like Str. potamida/chamaeleon, but I have seen S. potamida larva only once, and S. chamaeleon none, to say something about the variability. The habitat may be typical for these species. In both species the tip of the anal segment has typical hairs in front of the floating hairs. If you're able to collect these specimens (or better still breed them), I would be very happy to have a look at them.
Best wishes
Ton aka atylotus