Algae Free Hammerhead Float Algae Magnet for glass + I purchsed extra pads with out knowing it already came with an extra pad so you should never have to buy pads... ever...
http://www.marinedepot.com/ps_ViewItem~idProduct~AF1113.html
$60
http://www.marinedepot.com/ps_ViewItem~idProduct~AF1113.html
$60