If you get a bad scratch, you can use "micro mesh" (AKA "crystal bond") to buff them out when the tank is full. We had an issue where a "glass" pad was accidentally used on an acrylic tank for a swipe. Not the easiest thing to do. Rather than finishing with slurry such as Novus (great stuf BTW), I finished with 12,000 grit micro mesh (not a typo...12,000 grit). You can't even tell the tank was scratched.
Rather than trying to figure out what you need to buy separately, you can pick up one of those scratch removal kits, which has several progressively finer grits. Hint: make sure you always polish in one direction, then polish 90* to the previous grit. That way, you'll always be able to tell when all of the previous scratches are out.
BTW, we just use those white "made for acrylic" scrubber pads and those little red plastic scrapers (they cost about 89 cents at the LFS). For larger tough areas, I use a piece of 1/8" acrylic sheet (if I have some laying around).