Hey, i don't have a rodi system, i get it from the store just down the street, they have a huge rodi system and it's only 35 cents a gallon... as far as mixing the salt, i've always heard you're supposed to mix it and let it sit for 24 hours, but i mix mine and make sure that all the salt has dissolved and then immediately add it to my sump... probably not best, but it works very well, i've never had anything go wrong, but i'm kinda lazy as long as my tank is somewhere between 24 and 27 i'm happy (i keep it a little higher for the inverts)