I already know how to clean the outside of my aquarium. I take windex and wipe down the glass. What I'm having trouble with is the inside of my aquarium. A mystery substance keeps building up on the inside of the aquarium. I can't stand the look of it! I have to clean the inside of the glass at least once a week. I hate having to do it since my aquarium is 7' x 2' x 2'. Does anyone know what this substance may be? Any suggestions on how to stop it? I can't get pictures right now because I just cleaned it.