These questions are somewhat related. I'm about to switch over from tap water to RO/DI. I'm wondering if there are any circumstances under which it would still be necessary to use a water conditioner like Prime on RO/DI water? Also, how long can I let a new batch of salt water sit around and what, by the way, is the concern? Will it being to build up ammonia/nitrite/nitrate if allowed to sit over time? If I want to mix my salt a few days in advance of my water change, would it be a good idea to add some Prime to the water before using it in a water change?