I will use sensors from Atlas Scientific to measure the water quality of a sealed aquarium. The aquarium will consist of a nominally balanced ecosystem - shrimp, snails, plants, and other organic matter. The aquarium will be sealed to prevent exchange of air or other mass with the outside environment. With that constraint, the ecosystem can be monitored to see what effects the animals and plants have on the water. Changes in water quality may occur before changes in the rest of the ecosystem. If this happens, and these changes are repeatable across several closed aquariums, then there are clear implications for freshwater management. This project may also help improve the viability of closed ecosystems, including that of space colonies.