Observer wrote:
I have a rental house which just became vacant. I notice in the toilet
tanks, there is a mold / mildew problem. I'm not sure why since the
house a/c works fine. Anyway, what is the best way to clean this
inside the tank? I'm thinking of spraying bleach but I'm a little
afraid if that will hurt the plastic guts or rubber seals inside the
tank. Suggestions? Also any idea how to prevent this from happening
again over time?

I would pour a cup or two of bleach into the tank and scrub the inside
with the toilet brush. It should keep the mildew down for quite a
while. Mildew is probably as likely to erode the rubber seals as bleach
might; I wouldn't worry about it. If it is only a very light amount of
mildew, I probably wouldn't bother...I've never noticed mildew in my
toilet tank.