Fun in the Aquarium
Place two aquaria side by side, as shown in the diagram, and stock one of them plentifully with tadpoles. Then procure a length of glass tubing of stout bore and bend it to form a sort of bridge, as the one depicted in the picture. The tubing can be bent by heating it in a Bunsen flame and then pressing it as required. Place the tube under a tap of water and thus fill it. Close both its outlets with your hands and stand it in the aquaria as shown. The water will remain in the tube if the ends were plunged under the surface before you removed your hands.
With the bridge full of water, the tadpoles will dart up it and travel to the second tank. In fact, they will be making the journey, one way or the other, without ceasing. If you keep goldfish, you can make a bridge for them, too, but the tube will have to be considerably wider than for tadpoles.