The difference here is in the efficiency of the system.
And that this is an aquaponics system, which includes growing both fish and vegetables.

After more than two years of testing, Prof. Gross’s system demonstrated 1.6 times higher plant areal productivity, 2.1 times lower water usage and 16% less energy consumption per kilogram of feed than conventional systems. His calculations suggest that upscaling to about one ton of fish will allow operation of the system with no need for external energy, less than 1% water exchange, negligible waste production as well as significant carbon sequestration.