Don - I don't remember Cory's being big algae eaters?
I'm all on top of my diet. We cook so not a lot of processed food is served here. I do like my soba noodles. In checking labels I've seen the Sodium range from 60mg to 1250mg depending on the company.
If one wanted to feed Nori Seaweed, I really don't know if high sodium is even an issue for fish? The stuff I feed is marketed for Marine and Cichlids.
I'm also feeding it to my GoldFish. Of course that's about like feeding hogs. Anything you toss in they gobble up.