I knew I would have to sand the whole tank down and then buff/polish. Kicker was, I never did anything of this sort before, so I spend several weeks of research, asking question here and various other forums. It was actually slief's video on polishing scratches out of acrylic aquarium that I found on RC that got me thinking about this to begin with. If you havent seen these videos, and plan on doing polishing, you should watch them for sure
https://www.youtube.com/watch?v=Y8eTWZSNLWM
https://www.youtube.com/watch?v=dXthrMx7sq4
Since scratches were all over, I decided to sand down whole tank inside and out. I started with 400 grit sandpaper and used palm sander for the whole job. This thing was damn loud! I had to use ear plugs or else I wouldnt be able to hear anything for weeks.
Sanding outside was nice and easy and quick, however inside was a lot harder due to the brace on the top. It was hard to get in and properly sand it down, as I couldnt get good grip on the sander. It wanted to fly all over the place, so that wasnt fun.
Here is what tank looked like after 400 grit
Needless to say I was freaked out at this point, and thought to myself more than once what the hell have I done.
I went 400, 600, skipped to 1000 because I got different sand paper and their 800 felt rougher than 600 I used, 1200, 1500 and finally 2000. This took several weeks, as I was doing this after work. Since sander was really loud, I didnt want neighbors to complain, so I only did few hours every day or 2.
This is what it looked like after 2000 grit
I could at least somewhat see inside it, so I was happy to see it was clearing up as grit progressed. Next up was polishing and buffing...