I learned a very important lesson about my three goldfish the other day: never, EVER, under any circumstances, leave the tank uncovered. Not because the cat may eat them (which he might), or the kids might throw toys in the water (a very real possibility), but because of the danger the fish pose to themselves.
I don't know if it's insatiable curiosity, a daredevil attitude, or plain lack of a brain, but for some reason those crazy fish take every opportunity to leap out of their watery home and splat into the world of air to flop around.
Not just once.
Three times. Three times they tried to escape their aquarium. Yes, it took me this long to realize they were doing it on purpose. My theory is they want to move into a bigger place, and they're trying to check out the local real estate.