What I meant was, if you use tap water, which may contain chlorine, you can store it in the milk jugs, open to the air. Some fish do genuinely enjoy soft, acidic water, though. - like angels, discus, tetras,... I like the idea of a "hospital tank" and it doesn't hurt to have an auxilliary, cycled filter. With a hospital tank, you can move the fish and raise the temperature (as Prizmbatch cited) to speed up the life cycle of the parasite, as well as put medicines in, without messing up the main tank. Also, without a 'host', a parasite has nothing to kill.