[dknarnd]

Just moved into a new home and the toilet tanks are all lined with a black film; I'm going to change out the insides but what do I use to clean the inside of the tank?

 

[Mike Swearingen]

Rubber gloves and a little bleach or bleach cleanser ought to do it.
Mike

 

[RippySkippy]

The black could be from the deteriorating rubber componet. While your in there and have the tank clean...closely inspect the flapper, rubber washers that hold the tank to the base, and fill valve replacing any/all that need it. I doubt you'll even need any bleach...just a rag and clean water. I assume you're on city water? If not...I wouldn't want a large volume of bleach going into the septic system.