Heat from lamps above the experiment is absorbed by dyed, salty fluid, heating it up and making it less dense. This warm fluid rises, but the heat diffuses away, leaving dense, salty fluid in narrow vertical plumes. (Minor adjustments were made to brightness and contrast.)
(Accidental) double-diffusive instability —Megan Davies Wykes, University of Cambridge

Heat from lamps above the experiment is absorbed by dyed, salty fluid, heating it up and making it less dense. This warm fluid rises, but the heat diffuses away, leaving dense, salty fluid in narrow vertical plumes. (Minor adjustments were made to brightness and contrast.)

https://fluids.ac.uk/pictures/competition/3-double-diffusive_instabilit.jpg