We have been noticing several small black specs in our toilet bowl and learned they are probably mold. Cleaning the bowl found they quickly returned and this has been going on for over a year.
We thought that maybe mold is present inside the ceramic top drain lip where multiple drain holes flow flushing water down all around the toilet bowl. This inner chamber probably stays wet and is a mold breeding ground, but how to fix it?
We figured that we needed to get bleach into the toilet's top chamber and came up with a way to flush the area with ordinary unscented bleach, the same kind we add to our fresh water fill.
We removed the toilet spray handle and attached a short length of hose to the toilet sprayer hose, and added a PVC fitting to work as a funnel to pour bleach into. Photo attached
After our first treatment we noticed a dramatic reduction in black specs. Today we did another treatment and expect we may have licked the problem for a long time.
After pouring about 3/4 gallon of bleach down, we let it sit for many hours allowing the bleach to do it's job.