Medium Density Green Matala
The Green Matala 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.