I just went through this about a month ago. Small areas can be buffed out with the right equipment, but it is a long and tedious process and the guy I talked to would charge between $60 and $90 per defect. This guy was in Baltimore and didn't appear too happy to travel. You can get kits to do it yourself, including buffer. I never went to the point of asking the price of the kit. I look at it this way - a new 75 gal with overflow kits is about $250, a 90 gal RR $300, and 125 gal about $425. Unless you have a BIG tank and that one tiny scratch is just driving you nuts, Didn't you really want to upgrade to that bigger tank anyway? Seriously, cost, time and effort probably not worth the trouble.