Just a few metres from a busy road traveled by tourists visiting the Sakkara Pyramids a canal flows behind houses and apartment buildings to carry irrigation water along the farmlands and eventually out to the desert for reclamation projects. In the canals there live fish of various sizes, frogs and toad pollywogs, birds of all types and a newcomer to the area, crayfish. An enterprising fish farmer thought he was buying fresh water shrimp but when he saw his purchase, he dumped them into the river. Since then, about 15 years ago, they have multiplied like rabbits with a lovely side effect. The crayfish are especially fond of snails and have been devouring the snails that have carried bilharizia with the result that this parasitic organism has decreased 95% in parts of the canal and river system. But the crayfish are tough on the nets that the farmers set out for perch, so one of the men working in a boat is fixing his nets, while the others by the bridge are fishing water hyacinths and the ubiquitous plastic bottles out of the water.