This is an interactive biophysical model that shows the CO2 levels in an aquarium, as affected by photosynthesis, and plant and animal respiration. It is an aquarium with water plants equipped with a CO2 meter. Participants can watch in a matter of seconds as the plants uptake the carbon dioxide in the sealed system. They can breathe into the aquarium and watch the CO2 levels skyrocket. They can record the levels as the plants respire overnight. They can add a frog, or a candle to the system as record the effects. Having a hands-on feel for the effects of life forms on the atmosphere is an important aspect of understanding human impact and the dynamic nature of the atmosphere.