I use a 50 gallon glass tank to make and mix my saltwater. I have a Kent RO/DI for the fresh water. I dump a 50 gallon bag of Marine Enviroment into the tank that is almost full. This fills it to the very top. With about 5 mins. (using a mag12 to mix) it is ready for a water change. PH 8.3, Calcium 430, Alk 9.0 and SG 1.025.
Jim