Increasing aquaculture in China raises many challenges: lack of water, water pollution, eutrophication and fish diseases. To overcome these challenges, the Swedish company Wallenius Water AB provides so-called RAS systems (Recirculating Aquaculture Systems) for disinfecting and save water technology. In the joint project between Sweden and China, RAS is being implemented for fish aquaculture and in co-operation with Tianjin Normal University and Tianjin Fishery Institute. The ACESx is also a partner in this consortium. Using new methods for testing disinfection success, we help to build a RAS system operated in sustainable manner, with minimal negative effects on environment and maximal cost-efficiency.