The actual filter does come out - not the black housing box, just the filter. Have you ever cleaned the filter media? To take out the filter, first disconnect the outlet pipe, then just pull out the filter (don't forget to turn it off first). The filter itself is in 2 or 3 parts depending on what size tank you have (larger tanks with larger filters are 3 parts). Take the filter apart, clean the parts in tank water (not in the tank), put back together and put it back in the filter house. Connect the outlet pipe and job done.