I have a 75 gal RR that has been running for years. In the last few months, I had a breakout of a red algae (not red slime) and that has been resolved. However, on the inside front glass only, there is a film that is not really a color but is not true clear as you would expect glass to be. I have tried algea scrubbers, razor blades, other scrapers and no luck. I had a LBS friend service the tank for 6 weeks when I was on travel and he could not get it off either and had no idea what it could be. Any thoughts or suggestions how to get rid of it?