For Feeding Nori Sheets, I discovered this (
MAGENTIC FEEDER/GRAZER) a while ago, and will never go back to Elastic Bands, Clips ,etc.
https://www.marinedepot.com/Innovati...FDFECF-vi.html
The fish, snails, crabs have to peck at it to get their meal, but little/none gets out. You can place it low to allow your crabs to get to it, or high for Fish/SNails only.
I have 2, and
to me worth every penny since it contains the NORI well, so no loose stuff floats around your tank POLUTING IT, or unsightly stuff swirling in current..
It wastes a tiny bit at the Pinch points, but I just rinse it off and refill.
Never tried it with Macro Algae but I figure it will work if you squish some in, and then wrap a elastic around the Flap.
But don't expect to fit much since its a flap designed for thin Nori sheets.