A zero-discharge aquaculture system and process for treating water therewith, the system comprising an aquaculture tank (10) and a water treatment section comprising a foam fractionation unit (20) downstream the aquaculture tank (10) an anaerobic pond (30) downstream the aquaculture tank (10) an algae pool (40) downstream the foam fractionation unit (20) and the anaerobic pond (30) a common pool (50) downstream the algae pool (40) a bio-filtration reactor (60) downstream the common pool (50) and an oxygen injection unit (7 ) downstream the bio-filtration reactor (60) and upstream the aquaculture tank (10). The anaerobic pond (30) comprises an oxygen concentration reduction portion (36) upstream a pollution anaerobic treatment portion (38). The oxygen concentration reduction portion (36) comprises at least one oxygen concentration reduction member (31) positioned across a width of the oxygen concentration reduction portion (36). The oxygen concentration reduction member (31) comprises a network of oxygen removal agent support members (314) for providing a surface for an oxygen removing agent and defining spaces (316), wherethrough water can flow and come in contact with the oxygen removing agent.
