The first thing that comes to mind is a toilet paper oil filter. For those that just did this
, that is an old school oil filter where you would actually drop a full roll of toilet paper into the oil filter canister and screw it on. It was said to be the best oil filter you could get.
That said, I think it will work but you also have to consider the posibility of bio-loading. Of course you will want to filter mechanically prior to introducing the water to the bio-media, but I think this will work.
What is the cost vs. pot scrubbers?