in using this, you want a ...

in using this, you want a biofilm to develop.  basically you are feeding grey water to grow the geobacters in the soil.   otherwise the water coming out will still be dirty.   once it clogs, just rake it down.   to combat clogging just use the proper size of sand filter.  the larger the sand filter, the more time the microbes can clean the water.  a week long slow sand filter would have much less clogging than a 2 day sand filter.

hope this helps.  good luck