Flowtoys Flow Wand String has been specially chosen for its strength and lack of visibility to be the ideal string for your flow wand (aka levistick).
It's actually extremely durable ice fishing line and is supplied in a length of 5.5m (18'). Typically, a length of 1m (39") is used on a standard short-stringed flow wand. Long-string flow wands use strings of about 2.75cm (9') in length.
The gang at Flowtoys tested white, silver and grey string but found the black to be the least visible as it didn't catch the light like the other colours. We recommend not using magicians' invisible thread as this isn't strong enough for active levistick play.
Here's a video to guide you through re-stringing you flowwand: