A unique indoor filtration system that uses bacteria to raise marine fish has been developed by the Hebrew University's Department of Animal Sciences - an environment friendly alternative to the aqua-culture cages commonly used for fish farming in Eilat and around the world, which damage coral reefs and coastal waters. The experimental process, developed by Dutch-born Prof. Jaap van Rijn and colleagues at the HU Faculty of Agricultural, Food and Environmental Quality in Rehovot, has been patented by the HU's research and development arm, Yissum Ltd., and is being commercialized by a company near Karmiel. Van Rijn told reporters visiting the Rehovot campus on Monday that the patented technology allows the growth of certain kinds of bacteria in the vats, which do not have to be added to the water. The new technique makes it possible to raise marine (as well as fresh water) fish in vats containing tap water, which does not have to be changed - it merely has to be topped off from time to time to replace some water lost by evaporation. The bacteria are allowed to develop naturally in the vats depending on the rate at which the water circulates. As a result, it will be possible to grow one kilo of fish using only 40 liters of fresh water, instead of the 5,000 liters used in conventional outdoor fish ponds, van Rijn said, adding that a single one-meter tall vat with a two-meter diameter can be used to raise 400 kilos of fish. Ornamental sea fish made popular by the animated movie Finding Nemo and sought by aquarium owners, he said, can also be raised in the vats. During the campus tour, HU faculty members also spoke of other developments, such as the use of cloning to accelerate the growth of trees, and inserting electrodes into sewage water to improve the cleaning of wastewater for irrigation. A full report of the visit will appear on The Jerusalem Post's Science & Health Page on Sunday, May 21.