@zoalover tell me if you want to split an order.
Cerium oxide is a fine powder that has same hardness as glass. So you can use it to "polish/buff" out the glass surface. Of course, you'll probably also remove some glass material in the process, but as long as the etched glass is not deep scratches, it should work fine.
Read it works on glass, not sure how it'd work on an acrylic tank.
http://www.bostonaquariumsociety.org/html/faqs/scratches.htm
http://www.livingreefs.com/removing-buff-scratches-160-gallon-t22495.html
I was hoping a fellow reefer had some I can use instead of paying $30 for 1 lb, which is probably overkill for me.