i use the silver grade for my catering company...but then agian that might be why the company is considered a high class resturant.
anyways the hardness should increase with the salt content because hardness is just chemicals/stuff parts per water right? i know if i add aquarium salt it increases my hardness by a bunch that's why i was thinking of testing it like that. i just dont know of the actual nori would make the readings higher. i guess i'll try it out with my cherry shrimps first and see what happens. then afterwards test out with more expensive shrimp
