Abstract: A method of mitigating plankton from fish pens moves denser cleaning water from a selected depth into the pen and discharges it to flow horizontally across the pen, but with a downward component and at a sufficient velocity so that the cleaning water sweeps (carries) the plankton from the pen.

Abstract: A debris separating system for separating debris in a fish tank is formed by a standpipe extending up through the bottom of tank at the center of tank and terminating in an open end. A cover covers the opening and is spaced therefrom to provide an inlet opening positioned above the bottom of the tank. A transition zone is formed at the bottom of the tank surrounding the standpipe and a debris outlet is provided from this zone through the bottom of the tank for removal of debris separated in the transition zone. Cleaned water from the transition zone flows up around the standpipe, through the inlet opening and into the standpipe for removal from the tank.

Abstract: A debris separating system for separating debris in a fish tank is formed by a standpipe extending up through the bottom of tank at the center of tank and terminating in an open end. A cover covers the opening and is spaced therefrom to provide an inlet opening positioned above the bottom of the tank. A transition zone is formed at the bottom of the tank surrounding the standpipe and a debris outlet is provided from this zone through the bottom of the tank for removal of debris separated in the transition zone. Cleaned water from the transition zone flows up around the standpipe, through the inlet opening and into the standpipe for removal from the tank.

Abstract: Tank cleaning system is formed by an upper deck having a spout potion and a deck portion, injectors and a separation chamber having a conical bottom wall and a top formed by a waste baffle. The injectors connect the deck portion with the separation chamber so that the waste baffle and upper deck are axially separated to provide an outlet passage therebetween. The injector passages direct water through the upper deck and waste baffle into the lower chamber and impart a significant velocity component tangential to the chamber to the water flowing therethrough to impart a helical flow to the water in the chamber. A debris outlet passage is provided adjacent to the bottom of the lower portion of the chamber. The dirt laden stream enters the chamber through the injectors and dirt is separated by centrifugal action in the chamber and rejected through the debris outlet while the cleaned water passes through the outlet passage and is returned to the surrounding water.

Abstract: Tank cleaning system is formed by an upper deck having a spout potion and a deck portion, injectors and a separation chamber having a conical bottom wall and a top formed by a waste baffle. The injectors connect the deck portion with the separation chamber so that the waste baffle and upper deck are axially separated to provide an outlet passage therebetween. The injector passages direct water through the upper deck and waste baffle into the lower chamber and impart a significant velocity component tangential to the chamber to the water flowing therethrough to impart a helical flow to the water in the chamber. A debris outlet passage is provided adjacent to the bottom of the lower portion of the chamber. The dirt laden stream enters the chamber through the injectors and dirt is separated by centrifugal action in the chamber and rejected through the debris outlet while the cleaned water passes through the outlet passage and is returned to the surrounding water.