Filter Bag - Micron Size and Type

[CheyDogFlies]

What size of bag is too small or too large to use? I've been using 100 micron for the last 2 months, which I like so far, but I would like to try some other sizes. I read (on this forum, I think) that someone uses 25 micron and gets outstandingly clear water. Is there a size too small that will catch all the plankton, etc and be detrimental?

I have been cruising the filterbag.com website and see that there are also different types of mesh material: polyester multifilament and nylon monofilament. Do you guys know if that means anything to us, the marine aquarist?