The inside of plastic bottles used for pet waterers turn green with mold despite the addition of Microban in the plastic.  Removing the hazy mold from the larger bottles, especially those used with the Petmate Le Bistro 2.75 gal waterer, is next to impossible.  Because of the bottle configuration, bottle brushes can't access the area just under the opening where water comes out.  Filling a 2.75 gal. container with water and mixing in 1/4 cup of Clorox Bleach and allowing it to stand overnight kills the mold.  Unfortunately, even with several rinses the bottle still smells like Clorox (and probably tastes like it, if it's anything like pouring a gallon of bleach into my well every year to kill bacteria ).

Perhaps Clorox could develop a pet safe, pre-measured liquid product that could be used in these bottles and would kill mold, reduce bacteria, and not have a nasty aftertaste or smell.  Users could mix the product with a specified amount of water, depending on the size of the container, pour it into their pet's watering bottle, shake it, pour out the solution, then rinse the bottle and refill with clear water.