Was cleaning my filter using a pirana solution. Set it to drip into a flask. When looked inside saw drops spread out and rush back in towards the center. You can see it on video here: https://www.youtube.com/shorts/h6cOTa4TSNE
looks like the video is in reverse, but it is not.
EDIT: Most likely the explanation is as simple as: the little droplets are bouncing off the walls of the flask and back to the middle, because the effect stopped once some fluid accumulated near the perimeter, still kinda cool to see.