I have owned a Magnavore for 3years and it's worth every penny. I have used the same one for glass and acrylic. There is an additional pad for acrylic. The strongest magnet cleaner I have seen. DO NOT LET CHILDREN GET THERE HANDS ON THEM. They can break fragile fingers. And they do not float but take alot to remove from any surface. Also do not let the two pieces touch or you will have to send them back to the company to seperate.
The new ER (extended reach) Magnavores do float and they are great. The ER feature has the inside part extend beyond the outside part (larger) on one side. This allows you to get up and behind the tank frame at the top.