Wait...NuFoam is treated with a chemical? Are you sure? I have been using it in my pond filter for several months now, and I checked it out online first. It is being used by quite a few people in aquarium filters and ponds...
My fish seem to be doing fine so far, but it's only been a few months.
To the original poster, I can offer some suggestions on this type of product that do not relate to the chemical additive questions, but more to the "structural" issues. The batting (sheet-like) stuff can be cut to fit, but the loose cottony version must be securely contained somehow. I use nylon stockings, stuffed with the polyfill, and tightly knotted closed. If it gets loose, you will be pulling it out of impellors, plants, and fish gills. NOT good.
Also, hold a sample under running water and make sure that water will pass thru it. I had one batch that turned out to be impervious to water! That would have been a mess.