Sorry, not a good enough explanation...I have seen all three filters inside the tank. The filter disc is extremely fine, the sock is fine, and the pump discharge "injector style" filter is of xx micron (don't know the filtration specifics, but it is VERY EXTREMELY FINE

).
If there is enough dirt in the external filter, with it's comparatively huge surface area, to cause problems, what pray tell, do the internal filters look like???
...Ed
