I got the same response from TLF. The truth is, they cannot guarantee that. Unless they are paying a LOT for their magnets (they aren't), then the magnets are almost guaranteed to have impurities and trace metals in them, which, when rusting, become exposed to the water and can negatively influence your livestock.
I asked them why they don't just pot their magnets in epoxy... no answer. I conclude that TLF gives approximately 2 sh1ts.
What I do, take the plastic clip off the magnets, chuck the magnets, ziptie the clip to a rod hanging down in the tank, and insert/remove nori that way. I dont need magnets rusting in my tank to be yet another variable if things go south.
In other news, my wrasses love the nori too! I recently started buying it in Vons in the asian food section, you get like 5x as much for half the price as the "aquarium food specific" Nori, and it is the same stuff.
