Kind of like if you put a piece of paper on top of a full glass of water, put a book over that then turn it all upside down. Slowly lift the glass and the paper holds the water in by vacuum. I think we used paper, grade school was a lot of years ago. It could have been constructin paper.
i want 1 for a sa/ca community tank and hand feed them in the little bowls i would't leave the house.