Abstract: A secondary pool filter apparatus for use in filtering swimming pool debris and configured such that the filter can be substantially “flush-mounted” within a conventional pool skimmer channel so as to minimize the possibility of swimmers or other objects in a pool bumping into the filter. The filter comprises a liner having a main body adapted for removing floating debris from swimming pool water and a biasing element for enabling continuing operation of said skimmer system and to prevent the filter from backing out of a skimmer channel and floating or sinking. The filter main body and the biasing element are configured such that the filter has a substantially universal fit for use in many conventional swimming pool skimmer channels.