In order to stop the messages occuring in the logs you will need to right click on the problem Media Groups, select Properties, and then change the Low Watermark Level to 0.
With regards to the Cleaning Tapes, from the error message it appears as though your "Cleaning Tapes" media group is a Scratch Group instead of a Cleaning Media group. You may need to recreate it, set the media type to Cleaning Media, and then move the cleaning tape into that media group.