I use a 32g brute can for my setup right now. I am gonna be buying a new RO
unit very soon and was going to get another brute trash can and setup a real water making station. LOL I use one whole brute full of water for my 125g and another brute full for the rest of my tanks. I also keep 4 5g jugs of plain water stored in a closet indoors where its warm enough to use in an emergency. Hope i was somewhat helpful.
In fact right now I'm mixing water in the brute for some mad water changes in a few hours and I have a aqueon 250w heater that i put in when I put in the salt this morning and a koralia 750 mixing it. It seems to take less than 2-3 hours for the whole can to achieve my set temperature which is about 15-20 degrees warmer than the starting temperature of the water.