https://www.youtube.com/watch?feature=player_embedded&v=SDzJbhOVm0Q#t=14 https://www.youtube.com/watch?feature=player_embedded&v=SDzJ... Look at 0:14. This th

https://www.youtube.com/watch?feature=player_embedded&v=SDzJbhOVm0Q#t=14 https://www.youtube.com/watch?feature=player_embedded&v=SDzJ... Look at 0:14. This thing is put a little bit after the start of the pipe, creating a draft. The fish's own body becomes the "plug" that this air pump pushes up.