I would not put ANY chemical into the water you would not be comfortable drinking any amount of. Bleach is fine in trace amounts, it's used for sanitizing all sorts of food-grade equipment. However, CLR, etc are extremely caustic, and I would not be comfortable with even trace amounts in my water supply.
Why all the worry about some rust stains? I'll bet one TV dinner has more chemicals and bad bad things than you'd pick up from a month of use of the tank.
