Just a quick brief question that I used to know the answer to...but forgot a while ago. If you choose to keep a barrel of ready-made salt water for water changing so you can just get it once your ready to do water changing, how long does it usually take until the barrel of salt water expires (goes bad)? Because if it takes a very long time, this seems like an easier method of doing water changes than having to make salt water every week or every other week. Just a quick note as well: Im not planning on keeping cephs YET, but im upgrading my book on keeping cephs at the moment, which is why im asking. It's only a small tiny book just for MY reference.