I've got about 10 gallons of saltwater sitting in a couple containers right now...they're been there for about a week. I haven't had a need to use them, so they've just sort of been sitting there. I buy my saltwater at my LFS....I do not have an RO system at home yet, although I am considering! Anyway, I've been told that once you get the water, you should use it within the first couple days, otherwise it goes "bad". I fail to see how this is possible, but I'm no chemist and I'm not gonna take any chances. Are there opinions on this? Is it possible for saltwater to go bad after a few days?