ok so I went to the vet yesterday for my a problem with my ball (see post below). they gave me a paper on snake care, this is what it says about sleeping in the bowl. one of the most common problems we see at the hospital is snakes that are sick because they have been sitting for extended periods in unheated water dishes. if not given sufficient hiding places, or if they are shedding, or for a variety of unknown reasons, some snakes will crawl into their water and sit there for hours. as their body temp slowly drops lower and lower and lower, it eventually gets to the water temp (which is cooler than the air) and then the snakes gets very ill. if you snake does this, you need to either put in a dish that is too small for the snake to get its whole body into, or heat the water up to the mid-80's
hope that helps, can you tell I have extra time on my hands 
Misty
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