How can I effectively remove manganese stains from my toilet bowl?

To effectively remove manganese stains from your toilet bowl, you can use a mixture of vinegar and baking soda. First, pour vinegar into the toilet bowl and let it sit for a few hours. Then, sprinkle baking soda onto the stains and scrub with a toilet brush. Rinse thoroughly with water. Repeat the process if necessary until the stains are removed.