removing fine scratches from glass tank

[Saber]

Look under "lapidaries" in the yellow pages. They carry cerium oxide and many other polishing compounds for working with glass.

I have ground a few telescope mirrors in my life and use many types of grinding media for working with the glass blank. Last of which is cerium oxide, to finely polish the mirror before coating it.

You can remove the scratches. but be prepared for many hours of work. I do believe the lensing effect of grinding out scratches on the inside of the tank may disappoint as well.