Originally Posted by
aquaholic
In theory, having the moving bed filter(s) before a drum filter makes the most sense. In practice, due to high water flow rates, most people place the moving bed filter after the drum filter. Any dislodged moving bed biofilm has to go through the pond system to be caught by drum. I have bottom purge taps at the bottom of all my moving bed K1 barrels. I'm amazed at how much crap accumulates there.
I would keep your static bed filter after your drum as a polishing filter. If the drum works extremely well then you will not have to clean the static bed filter. Or you can remove it a couple years down the track.