The invention relates to fish farming plants (l), with adjustable horizontal flow speed, equipped with several movable permeable section walls (12) in each of the surrounding tanks (2), sothat each of the surrounding tanks (2) becomes divided into several adjustable tank sections. Where each surround tank (2) is equipped with one or two outlets (30) and that one or two inlets (29), regardless the number of tank sections. The fish farming plant (l) is constructed without pipe connections beneath the bottom level of the tanks (2, 3). The removable permeable section walls (12) are made with a frame and/or upper rod (23), which is automatically adjustable in the width of the tank (2), a permeable face (24) which likewise is automatically adjustable in the width of the tank (2) and goes from the rod (23) down to the bottom of the tank (2), and lower and upper wheels (25) placed in the bottom of the permeable face (24) and in the ends of the rod (23), respectively. The fish farming plans (l) is moreover made with a pipe connection to a purge tank (17), whereto the harvest ready fish can be brought without disturbing non-harvest ready fish, which can be done by reducing the volume of the tank section in question with the movable perme able section walls (12) and/or by light exposure of the harvest ready fish. The invention comprises furthermore the use of the fish farming plant (1) for produetion of fish, especially fish with a great need for high flow rate, and horizont al/laminar flow structure hereunder kingfish, salmon fish and mahi mahi, the plant is moreover especially suitable for produetion of grouper and barramundi.
