Peter I used to have the same issue using clips for nori. Here is what I did;
I had some left over brs 1/4" netting from my aquarium top. I cut a rectangle out and fold it in half. I then took a piece of rigid tubing and cut a couple "rods" out of it I then ran rods on each side of the netting going in and out. I then place a piece of nori in between the netting. I have a magnet that holds it in place on the glass. Works great! I still get the occasional nori floater but its not nearly as bad as before. Fish don't seem to mind it either. I can put up a pic when I get home if your interested in seeing.
Kris