Abstract: There is disclosed a cleaning apparatus for a radiation source assembly in a fluid treatment system. The cleaning system comprises: a cleaning carriage comprising at least one cleaning element for contact with at least a portion of the exterior of the radiation source assembly; a rodless cylinder comprising an elongate housing having a first longitudinal axis; a slidable element disposed on an exterior surface of the elongate housing; and an elongate motive element coupled to the driving element. The slidable element is: (i) coupled to the cleaning carriage, and (ii) magnetically coupled to a driving element disposed within the elongate housing. The elongate motive element has a second longitudinal axis that is oriented in a substantially parallel, non-coaxial relationship with respect to the first longitudinal axis.