Abstract: A buoyant, substantially egg-shaped fish farming tank with a shell with an internal farming volume, includes a substantially vertical main axis of the egg-shaped shell in the fish farming tank's operative, filled condition, the shell's blunter end being directed downwards, while the more tapered end is directed upwards, one or more inlets from the ambient seawater to the farming volume through a lower portion of the blunter end of the shell, and pumps arranged in proximity of outlets which are in proximity of the water surface of the ambient seawater, the outlets lead back to the ambient seawater, wherein the pumps are arranged to evacuate water from the farming volume.

Abstract: A farming tank includes a closed, rigid shell generally containing a farming body for aquaculture animals such as fish or shellfish, the shell being essentially ellipsoidal or egg-shaped and arranged to have a generally vertical main axis, and at least one internal ballast tank is arranged within the shell and at an upper section of the shell. The ballast tank has a radially outer wall which follows along a higher-lying section of the shell or is formed by a high-lying section of the shell itself, and a ballast pump arranged to fill or empty the ballast tank partially or completely with water via a ballast water pipe.

Abstract: A fish rearing tank has an egg-shaped shell with a vertical long axis and gradually narrowing shape towards a tip portion. The egg-shaped shell holds a water volume for the contained fish in a major wider, lower portion, and encloses air in the minor, upper, tip portion. The shell forms a closed, rigid tank and has one or more water inlets, and one or more water outlets. A ring-shaped buoyancy collar is mounted on the egg-shaped shell. The shell has a fixed ballast in the lower end of said wider, lower portion of the egg-shaped shell.

Abstract: A fish rearing tank comprising the features of: a) an egg-shaped shell (1) with a generally vertical long axis and gradually narrowing shape towards its tip volume portion; b) said shell (1) forming a generally rigid tank; c) said shell (1) being closed; d) said shell (1) having one or more water inlets (11); e) said shell (1) having one or more water outlets (16, 29); said egg-shaped tank (1) for holding a water volume in its major lower volume portion and enclosing air in its minor, upper tip volume portion (4). Further disclosed is a method of rearing fish providing such an egg-shaped shell (1) and conducting bottom to top or ?reverse?-circulation of water through said egg-shaped shell (1) while maintaining its air-filled volume in said tip (4).