Flying Fish?

Nicolas Leschke of Efficient City Farming in Germany is going to trial the setting up of aquaponic fish and vegetable farms on the roofs of buildings in Berlin (http://www.guardian.co.uk/environment/2012/jun/04/rooftop-fish-farms-german-population?INTCMP=SRCH). The idea is to reduce the distance that edible fish are transported as well as minimising the impact of fish farming on the environment by culturing Perch in roof-top tanks. The ammonia that the fish excrete will then be used to help grow tomatos etc. The only real question I have is, where will the food for the fish be generated (and from where will it be transported)? It is an interesting idea but the installations are unlikely to be odour free.