Medium Density Green Matala Mat can follow thereby trapping a medium size particle. Both Green and Black clean out very easily by simply shaking the pieces out before draining the sump.
When you use the Black or Green Matala for solids filtering you may use the garden hose to spray clean them. The dirt falls off very easily.
A good biofilter needs a lot of surface area with open spaces between for good aerated water flow. A high surface area is useless if the passageways are so small that water flow cannot penetrate.