LOL, it really depends on what you are trying to accomplish in my opinion
. While a filter sock may be ideal for some in some cases, it doesn't do the same job as carbon/GFO or a refugium.
No matter how you cut it though, *I* think a skimmer of some sort should be a part of one's filtration set up... depending on the size of tank anyway. A 2.5 gal nano really doesn't need one
.
So basically, what are you trying to accomplish? Mechanical, Chemical, a combination?
Chris