How to remove black mold in the toilet?

Use Clorox bleack to clean and kill the mold.

Well, this started out as a mission to find out the purpose of the styrofoam in the tank, the answers varied.

Some say it is a source of insulation (from what you ask-some say sweating from the tank and othes think it is from the sound of the tank flushing and refilling). Some toilets sweat based on the temperature of the water in the pipes vs the room temp.

Temperature variation=more or less water sweat.

Another source says it is there for a low water volume flush and it can be removed and replaced with something to displace what the approximate area it takes up (beer bottle filled with sand and capped). Just so nothing moves and gets in the way of the functioning parts.

There seems to be a general "no meeting of the minds" on this issue.

Best to you.

Hydrogen Peroxide

The foam is to insulate the toilet tank and prevent condensation on the outside....in theory. Vinegar will kill mold spores. Bleach is a cleaner it does not kill mold. Do not mix the two together. Best solution would be to remove the foam and clean the tank with vinegar.

I have never heard of this insulation method. Just remove it ... probably not necessary.

I agree with Barbara. I have never heard of styrofoam being left in the tank other than to prevent breaking during shipment.