I thought the Matala was primarily used as a bio filter because it provides a lot of surface area for bacterial to settle in with large pores for the water to flow through, so it doesn't easily get clogged. Which grade of courseness are you using? And do you have several sheets going across your barrel or how to have the material arranged, so that the water passes through it and doesn't merely go around it?
DJ keep in mind my pond filter system is new and un-tried and un-tested and I'm not recomending anybody copy it, not at this point anyway. but you asked what I was using so that's why I posted it.
It's probably true that many people use the Matala as bio filter media, and of course it would and does work as such, just like pop cans or anything with surface area woud work, but it also works as a mechanical filter. My thinking is that mechanical filtering should be done in stages, with that in mind a skimmer basket actually works as a first stage in mechanical filtering by capturing leaves and other floating debri that might otherwise clog your pump or any other finer filters you have in your system. In my case I have a settling tank that is suppose to capture other heavier debri coming from my bottom drain. From there the water exits near the top of my settling tank and flows into the tank with the 3 Matala filters. Those Matala filters are friction fit and arranged into progressively finer filters with the thinking that the largest one will only capture the large stuff that made it though the settling tank, and the next finer filter will capture the smaller stuff that made it through the large Matala filter, and so on. Having stages like that prevents the finest filter from getting clogged up to fast. I use the same system in my heat pump furnace air filter, I like to buy the expencive HEPA filters to filter our house air and keep dust from clogging the fine radiator fins in there. Problem is those fine HEPA filters are expencive and clog up fast because they are so fine and capture everything. So what I do is put a cheaper coarser grade filter in front of the HEPA filter to catch the big stuff first, thus prolonging the life of the HEPA filter. I can normally change the cheap filter twice before the HEPA filter needs replacing.
Probably none of those Matala filters would work well for filtering out the fine particles you have suspended in your pond, which I suspect are the dead and dieing aglea cells that tend to clump together when they die. I don't have that problem in my pond, not at this time anyway. If it does become a problem I'll probably add some finer filtering material, possibly in my bio-tank since I have lot of room in there and don't think I'll ever need much bio media if any. This is why I went so big with my filter system, to have a lot of room to play.
My other reason for using the Matala filters is their rigidity. This helps them friction fit into the barrel and not need any extra re-inforcement to hold them into place, also they should stand up well to repeated cleaning with a hose, or possibly a pressure washer. Other finer types of filter material are hard. if not impossible, to clean and basicly disposable, like furnace air filters.
