Things You'll Need
Instructions
Remove the lid from a clean, empty plastic margarine container. Trace the mouth of a 20-ounce soda bottle in the middle of the margarine container's lid, and cut out the hole. Pierce holes all over the the rest of the lid with a thumb tack. Put the lid back on the container, and measure its height -- from the base to the top of the lid.
Add 1 inch to the container height measurement, and cut off the same amount from the top of the soda bottle, using the knife.
Pierce a hole anywhere near the outer edge of the container lid, making it slightly smaller than the diameter of your air hose. Push the air hose through the hole from the outside of the lid. Connect the hose end extending from the underside of the lid to the aquarium airstone. Put the air stone, with the connected hose, in the bottom of the plastic container.
Place the cutoff part of the bottle on top of the air stone, with the mouth pointing upward. Fill in rocks around the bottle, up to the rim, and put the lid on the container -- with the bottle's mouth poking up through the hole in the lid, along with the air hose. Connect the other end of the air hose to the pump.
Place the container in the aquarium, and turn on the air stone. Watch air bubbles float up through the mouth of the soda bottle.