The first few seconds of this video may leave you a bit confused. The next few however are sure to bring the confusion on. Are those waterfalls? Are they under water? If they are water falls under water, what is falling? What the heck is going on?! At least that is what I thought during the first 10 seconds or so.
As it turns out, that is fine sand being pumped up from the botton and cascading back down. The effect is amazingly like a miniature waterfall. The white particles simulate the white water of a splashing cascade very well.
I found a link to a DIY thread for the effect. It is in chinese though, so I’ll break down the basic idea below.
these two diagrams show the gist of it. You have a trough, a tube, and an outlet. You pump water up the tube and it will pull some particle of sand with it. They then cascade out the outlet at the top and pour back to the trough on the bottom. The idea is pretty simple really, but when implemented well, the result is really impressive. There are a ton of process pictures of building one on the site, as well as a couple videos, so you should check it out.
initially found via reddit.
edit: just found this video tutorial!