A lice treatment system (and a method for a lice treatment) for fish comprises an inlet (1), a first separator (2), a pipeline (6), a second separator (7), an outlet (8) and a circulation pump (10). The inlet (1) receives the fish to be treated and the first separator (2) separates the fish from the water and the fish are then transported through the pipeline (6) including a liquid treatment bath (5) within the u-shaped part of the pipeline bordered by respective liquid surfaces (4). The second separator (7) separates the fish and the treatment liquid. The outlet (8) discharges the treated fish and is arranged after the second separator (7). The circulation pump (10) circulates the treatment liquid through the pipeline back from the second separator.
