Fixing scratches?

[hawk]

It will really depend on how deep the scatches are. If they are deep enough to feel, even in the slightest (use a pin to drag across the surface) you will need to grind them out way before you start polishing with any compound. Cerium oxide will be a final step in a very long process. In theory you can grind out scratches in any surface followed by polishing but the work involved in even minor scratches in glass is huge. Unless it is a very large tank with very minor scratches I would check into having the front pane replaced.