In the ECF Urban farming project in Berlin fresh water fish (perch) is cultivated in collected rainwater in an old factory building. The water, enriched with fish excretion, is then used for vegetable growing in the greenhouses. The advantage of this system is that it is almost a closed water cycle: the production takes place close to the consumer and there is hardly a need for transport. The waste product of the fish production is also used as fertilizer to grow the vegetables. The company occupies around 1800 m2 and delivers 30 tons of fish and 35 tons of vegetables per year.