I got the stirrer last week in the mail and immediately unpacked and played with it. This weekend has been a real bugger so I did not get the water tested
I did put on the beaker and created a couple cool water vortexes. I then (prior to reading the instructions) put on a large glass of water to see how big a vortex it could create I took a picture I'll post, but it was quite impressive at about 3.5". Disclaimer, the instructions say I should not put any container on it that is bigger that the stirrer itself so don't tell anyone.
I'll post back later after I test some water with it.