A skimmer filter assembly includes a hollow skimmer box including therein an accordion pleat weir-type water inlet, substantially vertically positioned filter mats and a submersible or external water pump positioned at the rear of the skimmer box. A filter mat holder and dirty sump retain the filter mats in a stable, slightly off vertical position and provide for removal of the dirty sump without repositioning the weir or water pump. The water pump is positioned in a portion of the skimmer box which is not vertically restricted, thus allowing multiple size water pumps to be utilized in their standard upright position without removing the mats to make room for large pumps and providing for servicing or removal of the pumps without disturbing the filter mats the filter mat holder, the dirty sump or the water inlet weir.