Zero Water Exchange systems that I have designed and managed work equally well for freshwater. Koi were purchsed from a local hatchery and stocked into a tank at 28 fish/m3, with an average weight of 33 g and within 6 months increased to an average size of 350 g and a biomass of 8.7 kg/m3. On 1-Dec-15 all fish were removed and weighed with pictures taken and posted below. The biomass had reached 10.7 kg/m3.