Cleaning tank glass with windex???

I would personally avoid it.

white vinegar.. no joke.. or spray the windex on a rag/towel in another room/away from tank and wipe w/ rag. White vinegar ime works just as well as windex if not better.. and you can pretty much dump it into your tank w/out harm ( Not that I would intentionally do it!) I've been useing it for years, works well to get the white residue that builds up on filters as well. any steaks left by vinegar are easily buffed out w/ your rag.

EDIT! Oddball beat me too it! lol

I've always used windex, I just don't spray it directly on the tank. I spray it on the rag. I also recently purchased a product made by API (Aquarium Pharmaceuticals). It's called Safe & Easy Spray. It's safe for use on the inside and outside of glass or acrylic tanks. I got it from petsmart because I had just purchased my previously-owned 125, gallon which had a lot of build up on it. The product works well, and comes in a nice spray bottle. The only problem is that it cost money, compared to vinegar, which is very cheap. After I run out of this product, I'll probably fill the nice, little spray bottle with vinegar. What can I say? I'm a penny pincher.

I often use windex to clean my aquarium glass. You just got to use a little common sense as to where your spraying it.