HI, Windex is fine but be VERY careful. Spray it well away from the tank. Try using water with a bit of vinegar mixed in. It works well. Not to much vinegar though or your room will smell like a french fry stand !!!
I always just spray a little right on the glass and have yet to have a problem. If you have a top/cover on your aquarium you should be ok. You only need like one little squirt anyways.