When National Aeronautics and Space Administration scientists were planning space colonies that would be self-sustaining worlds, they started small. They put a half-dozen tiny red shrimp in a sphere with a little water, some bacteria, a bit of algae, and a few plant strands. Then Loren Acker, president of Engineering & Research Associates Inc., of Tucson, saw the spheres and turned the experiment into a commercial product. Now available for $250 through such tony catalogs as Neiman-Marcus's and Hammacher Schlemmer's, the five-inch EcoSphere never needs food, fresh air, or new water -- perfect for the person who tends to love a guppy to death. It is a world small enough for your desk top. However, it has one fatal flaw. After 5 or 10 years, the shrimp die out, leaving no offspring. There are some things, it seems, even shrimp won't do in public.Picture, Loren Acker, president of Engineering & Research Associates, sells Eco-Sphere, a self-sustaining world inhabited by tiny shrimp. Gil Kenny/Black Star