I think properly allowing the salt to dissolve has a lot to do with things like letting it reach proper pH, proper ionic balance, temp., etc. I have a friend who never lets his newly mixed water sit with aeration or anything, he just mixes and adds it, and he has never had a problem and has some of the healthiest water I have ever seen. Myself however, started by mixing mine and allowing it to aerate and heat over night, so I see no reason to stop doing it my way. I have a big rectangular rubbermaid type storage bin that I use, I can fit 15 gallons in it comfortably, and I throw in a few air stones and my spare heater and allow my water to sit overnight before doing a water change.