If its glass: The rule is if you can feel it with your fingernail then it won't come out no matter how much you buff it. You really are only buffing it with the jewelry polish and if you have to question it then it's probably too deep.
If its acrylic: it can be easily buffed out but can leave a warped look if you buff it too deep. I've seen videos on YouTube where people lowered the water and covered with plastic. It seemed to work but I wouldn't try it myself. I wouldn't want to drop any chemicals in the tank
I've done a 125 empty, it was a pain took a few days to do the while tank going through 4 or 5 different grits of paper then polish. Doing it full might be somewhat easier as the water seems to hide the finer scratches.
I have a service guy that might do it but I cant say that for sure pm me if you want his info he did a quick buff of my cubicles and they were pretty bad and it made a nice difference thx