Daily Water Changes

[rocketlily]

I am currently reading the book, Marine Reef Aquarium Handbook, by Dr. Robert J. Goldstein, and he recommends a daily water change of 1 percent for a tank 100 gal (1 gal) or for a tank half the size, change a gallon every other day.

My question is, that for a 20 gal nano tank, when you should be changing 2-3gal per week, would it be better for the tank (in a perfect world) if I changed a litre per day. This also brings me to my second question. I am using Red Sea Coral Pro salt for RO water. How big of a batch of water can I mix and how long can it sit before using. Can I mix 3 gals. in a pail, cover it and use it all week for daily changes?