Abstract: An aquarium system is made self contained, even for salt water, by providing it with a sub-gravel filter in series with a carbon filter, and ultra-violet sterilizer and a temperature control unit, and a water withdrawal and return that insures circular flow in the tank. The system includes a means for introducing outside air into the filter circulation system, advantageously at a point just prior to reintroduction of the filtered water to the tank. Capability of the system to provide an environment in which long-time survival of sensitive fish and invertebrates is made possible by the addition of an air stripper unit in parallel with the sub-gravel filter. The air stripper and the ultra-violet sterilizer are specially constructed to enhance the operation of the system.