The EcoSphere is sealed blown-glass miniature aquarium produced by Ecosphere Associates, Inc., of Tucson, Arizona, United States. Spherical or ovoid, the aquaria range from roughly baseball-size to soccer-ball-size. They are sold worldwide as scientific novelties and decorative objects. The spheres are populated by tiny red-pink shrimp, which swim energetically around the aquarium, eat the brown bacterial and algal scum on the glass, consume the filamentous green algae which sometimes forms a globular pillow in the water, and perch on a fragment of coral.

Each EcoSphere is a materially closed ecological systems which is self-sustaining over a period of years. At room temperature, and with only low inputs of light, the algae produce oxygen which supports the shrimp and bacteria. Bacteria break down the shrimps’ wastes. The breakdown products provide nutrients to the algae and bacteria upon which the shrimp feed. The manufacturer states that shrimp live in the EcoSphere for an average of 2 to 3 years, and are known to live over 10 years.

The coral is dead and plays no active biological role in the system, however it does increase the surface area for beneficial bacteria and algae, and the calcium carbonate in the coral acts as a pH buffering agent.

A magnetic scrubber is enclosed in each EcoSphere. By passing another magnet over the outside of the glass, the owner can manipulate the scrubber to clean the inside of the EcoSphere. Prior to 1997, the EcoSpheres contained at least one snail at the time of purchase, which would clean the glass (but they were removed to make the sphere self-sustaining).

It is possible to purchase Halocaridina shrimp from Hawaiian aquarium dealers and create home-made sealed aquaria with no other special supplies. Sand, gravel, crushed shell, and very well cycled filtered water from a successful saltwater aquarium, with the lowest attainable ammonia content, should be used. A small inoculation of live Spirulina algae may be introduced. Certain ubiquitous algae and bacteria are likely to be carried by the shrimp themselves and will soon colonize the walls of the container. There is a risk that pathogens also may be introduced.

Every manmade closed system inevitably degrades. The EcoSphere and comparable closed systems are actually ‘self-sustaining’ only in comparison to systems which degrade much more quickly. In any closed, unfiltered, unaereated aquarium, it must be expected that the larger organisms will reach the end of their lifespans, die, and pollute the water with a sharp influx of decay products; or the nutrients in the food cycle will gradually get ‘locked up’ in unusable forms; or the pH of the water will fall outside the survival range of the organisms. The EcoSphere is remarkable in that its degradation is so slow, supporting relatively large, complex organisms (the shrimp) for years, cycling nutrients many times.

The advantage of an aquarium closed with a lid (rather than a permanently sealed plug, which is found in the base of an EcoSphere) is that if the system goes out of equilibrium, the owner can remedy conditions and prevent a complete die-off. Intervention to maintain good water quality allows a larger number of shrimp to live in the open system than can survive in the relatively poor quality closed environment.

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