Ferrofluid displays are adjacent to cymatics rather than part of it. The fluid responds to a changing magnetic field from a coil driven by the audio, not to the sound pressure itself, so the shapes are magnetic rather than acoustic. Worth being clear about, because the two get filed together constantly.
As a build it is thorough. The description links a tutorial page, the schematic and the parts list, and the 3D print files are available, so this is a design you can actually reproduce rather than admire. Twelve minutes covers the enclosure, the coil, the Bluetooth audio board and the fluid handling, which is the part most people get wrong — ferrofluid stains glass permanently if the carrier chemistry is off.
Useful for a studio that already works with driven fluids, provided you file it under magnetics.