Not sure what you consider expensive but I love these http://www.bulkreefsupply.com/algae-free-magnetic-glass-cleaner.html
I have never used this on acrylic myself only glass but it has pads for both.
Won't take off coralline though
End shots
[IMG]http://i1295.photobucket.com/albums/b638/Denniseric2/image_zps56a1dda5.jpg
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