My AquaMag Nori Seaweed Feeder is something I developed out of need. Standard "veggie clips" were not able to hold onto my Nori long because as soon as Nori gets wet, it gets soft & my fish would rip it off a clip in 2 seconds flat! Then the Nori pieces would bumble around the tank only to go to waste!
My AquaMag is 2x4" which fits the Nori I sell when folded. Made out of 1/8" Lexan it sports 2 rare earth magnets that are epoxy coated making them reef safe. Attached is filament line so you can determine what depth to hang your feeder. I recommend hanging 1/2 way down the glass on one tank end. Also comes with a rubber band. I recommend making one full wrap length-wise then 2 side wraps to really hold the Nori in place. Rubber bands are neutral & will not harm the tank even if they break & get out of reach. They will just break down & not bother anything.
Bewarned! The magnets are very strong & can pinch fingers! This is Not a toy. Use with caution.
Pictured here is a 1/2" thick AquaMag. They are now 1/8" Lexan, plenty strong & less expensive!