Couple of possibilities. The first is a razor blade; just scrape it off. If that doesn't work paint stripper. Zylene will remove latex in much the same way that paint stripper removes oil based paints. Most paint doesn't stick that well to glass so it is usually not that hard to get off. If you are using a stripper, or the Zylene, do it out side, as the fumes are noxious and dangerous.
Join a fish club.Don't have one near by? Start one.