Do you know what's the Ferrofluid?
It's a magnetic liquid that becomes strongly magnetized in the presence of a magnetic field.
So what's the point having a ferrofluid tube? It's one of those things that once you start playing with it, you can't stop!
So take a look at these original Kickstarter project, the Ferrofluid Magician, it's perfect for a gift or for your own pleasure!