Hi all -- I want to post to this because I am having great luck using quilt batting as a complement to our waterfall weir filter system (we also have a skimmer, but I don't use it there).
Here's what we do:
* Make a paper template from the original filter pad that came with our Savio waterfall weir. I'm sure this can be adapted to most types of filters. (I have also made additional 'regular' filter pads by cutting my own from bulk media on a roll purchased at our local pond store. We rotate our filter pads as they need changed, then use a pressure washer or garden hose to rinse all the gunk out (of the regular ones) -- hang to dry and keep in rotation.)
* Go to a fabric store and purchase (watch for sales) the thickest polyester (not cotton) quilt batting I can find on the large rolls - I get the stuff that's close to 1" thick, ~54" wide, and purchase at least 2 yards long so I can make several at once (you can estimate how much you need based on your own filter pad size).
* Using your template, draw around it onto the quilt batting with permanent marker and cut as many supplement filters as you can. The more the merrier.... they are reusable, and you won't run out as you change them out.
* I take ONE of the cut quilt pads (I've used as many as two if they're thin) and place it OVER the main filter pad in your gizmo. The
reason I place it over and not under is so that the main filter can catch the bigger stuff first, and let the finer weave quilt batting catch all the fine particles that would normally go back into your pond.
* You will need to
WATCH the filter a lot right at first because it tends to clog up frequently because of all the fine stuff it's catching. I've had some overflows... That should ease up a bit after awhile. I also don't leave the finer filter

in overnight because of the same reason. You'll just have to play with it for your own situation.
* Now here's the gross but interesting part....

I save all the used (and incredibly gross) quilt filter pads in a bucket until there's enough to wash out. I use my washing machine on a gentle wash, and if you have any zip laundry bags, that will help them not get too beat up. You'll probably want to do this several times until you're happy with how clear the rinse water is. Be prepared for some seriously gross thick nasty black water while you're doing this! (NOTE: DO NOT USE DETERGENT OR BLEACH - just plain water!) I've washed my current set of quilt filters many times already and they are still holding up well. Then, just hang outside or in the garage and dry and recycle as many times as you can. (If that grosses you out using the washer, than you can alway run it through a bleach cycle when you're done...
I've notice a huge improvement in our pond clarity and I can't help but think that getting all the fine particle nasty stuff out of the water can only help. Someday maybe we'll have a bio filter, but until then..