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).

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).

An apparatus for cleaning nets underwater comprising a cleaning head formed from at least one propeller having a perimeter rim available for receipt of fingers, knuckles and/or torsion spring elements. The cleaning head is positioned against the surface of an underwater net wherein the cleaning features are constructed and arranged to remove soft and hard growth from the nets.

An aquarium cleaning device includes an isolation zone forming member having opposing first and second sides. First and second liquid passages are formed through the member between the first and second sides, each of the first and second liquid passages having an opening on the second side. A gasket is secured to the isolation zone forming member and forms a loop around the openings of the first and second liquid passages. The gasket is disposed to create sealing contact against an aquarium wall when the isolation zone forming member is held against the aquarium wall. An input tube is fluidically connected to the first liquid passage and an output tube is fluidically connected to the second liquid passage.

An aquarium cleaning device includes an isolation zone forming member having opposing first and second sides. First and second liquid passages are formed through the member between the first and second sides, each of the first and second liquid passages having an opening on the second side. A gasket is secured to the isolation zone forming member and forms a loop around the openings of the first and second liquid passages. The gasket is disposed to create sealing contact against an aquarium wall when the isolation zone forming member is held against the aquarium wall. An input tube is fluidically connected to the first liquid passage and an output tube is fluidically connected to the second liquid passage.

Closed tank for fish farming, in which the tank is equipped with a liquid tight housing and a water supply system, a water discharge system and at least a particle discharge means, the water supply system comprising a plurality of vertical inlet pipes which serve as a load-bearing element of the tank. The inlet pipes and a vertical pipe and interconnected pipes may constitute a load-bearing skeleton. The tank may have separate buoyance chambers dimensioned to provide sufficient buoyance even if one chamber should fail, and one chamber in contact with the water in the tank arranged to be filled with and drained of air, to thereby reduce and increase the water level in the tank.

The aquarium vacuum is a cleaning device adapted for use with aquarium. The aquarium vacuum is adapted for use in cleaning algae from the walls and corners of an aquarium while water is in the aquarium. The aquarium vacuum comprises a scrubbing device, a pump, and a filtration unit. The scrubbing device is used to remove the algae from the aquarium wall and corner. Algae released from the aquarium wall is drawn into the filtration unit with the pump. The filtration unit removes the algae and other particulate matter from the water before returning the processed water back to the aquarium.

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).

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).

A water change system includes an elongate tube and a spout configured to be coupled to the elongate tube. The spout includes a first opening and a second opening spaced from the first opening. The spout is rotatable between a first position to permit water to enter the second opening and pass out of the first opening, and a second position to inhibit water from entering the second opening.