Cultivation tank for aquatic organisms

A device with a tank for the incubation or cultivation of aquatic organisms, said tank including a side wall and a bottom, a supply pipe into said tank for the introduction of water, outlet pipe means for water, excess feed, excrement, dead eggs and the like, a suction unit within said tank and connected to said outlet pipe means, said suction unit comprising at least one moveable suction arm operable adjacent said bottom, said at least one suction arm being positioned such that when in motion an area approximately corresponding to the shape and size of the bottom is covered, said outlet pipe means including air inlet means for controlling outflow of water through said outlet pipe means from said tank at intervals, said device also comprising a combined float and weight means in said tank above said suction unit and vertically moveable up and down in response to changes in the level of water in said tank, and cooperating means on said suction unit and said float and weight means for transformation of downward movement of said weight and float means into movement of said at least one suction arm, said downward movement of said weight and float means being in response to downward movement of the water level in said tank as water and waste products are outwardly drawn through said at least one suction arm.