Abstract: A plurality of elongated tube cleaning element capturing cages of different lengths are mounted within the heat exchanger chamber. The cages are so constructed and positioned so that fluid discharging outwardly from the cages flows laterally in a plurality of transverse planular layers. Fluid discharging laterally through the openings of the shorter cages impinges against closed wall portions of the longer cages, with the openings of the longer cages being disposed axially beyond the openings of the shorter cages. The longer and shorter cages may be arranged in substantially alternating relationship. In the event that some longer or shorter cages are disposed directly adjacent each other, openings of adjacent similar length cages are disposed in generally facing relationship with imperforate portions of the adjacent similar length cage.