I'm pretty sure she was talking about cleaning out the physical filter (the hardware).
If that doesn't work, what I woudl recomend doing is measure the nitrAte daily. When you figure out how long it takes for the nitrate to raise 20-30 ppm, it is time for a water change. Having your tank over stocked will mean you have to do a water change. Also, until you get this under control, cut back on how much you are feeding your fish. That will cut down the waste in the tank.