pretend your a hippie, and your gonna macrame your hair into a plant holder...
nevermind, different project...
o.k. first off your going to have to take your pump apart..
take the impellar out,
then your going to have to take the top 1 of 2 layers of the needle wheel off, either by prying it off with some needle nose pliars, or you could dremel off the needles(see pic 1)
then you have to attach probably 2 layers of mesh to the impellar. remember to cut a little hole in the center of the mesh so the impellar post will fit, and fasten with the smallest size of zipties to the bottom half of the needle wheel impellar.
then your going to have to trim the mesh down to the size of the remaining needles, and probably a little off the top. you dont want it rubbing or dragging on the pump housing at all. it should look like this when your done(pic 2)