Thanks everyone.
I use the roasted Nori, but I read that "roasted" isn't the best for feeding fish. I guess the roasting process might remove nutrients from the seaweed. But that is just a "guess" on my part, I'm not sure that roasted Nori is nutritionally deficient. I used to feed Romaine lettuce but not anymore. I'll keep looking for plain Nori but until I find some I'll just stick with the roasted Nori. My fish really love it.