you talkin about those white calcium/mineral deposits on glassnear the water's surface? I've been wondering how to get that stuff off. it doesnt come off by scraping it with alage scouring pads...maybe vinegar?
Vinegar works pretty well. I've also used a product called Lime-Off (by Jungle, I think), which is made for aquariums, that works really well. I have extremely hard water, and vinegar isn't always strong enough for a large buildup.
I have the hugest amount of that stuff on my old 10g, it's disgusting! I am going to have the biggest cleaning job everr if I plan on using the 10g again.