is it like a milky white color or an rusty brown color? the glass on my tank hood is realy hazy, milky white stuff that i cant seem to remove no matter how many times i have tried washing it. if it is a rusty color then use bleach, NOT ALOT! and fill the tnk with water and let it set overnight or up to 2 days, without fish or gravel or anything else and then rinse it about ten times keep wiping the tank fully with a towel, and make sure there is no bleachy smell left in it. but if it is the milky white stuff im at a loss as how to remove it.