I bought 12 gallons of Rodi water. i put in 6 cups of instant ocean salt and the refractometer reads 1.018ppm. Ive had it mixing with a power head all day. The water is pretty cold though because I only have one heater thats in my tank atm. Should i add more salt? Should I wait longer for the salt to dissolve? Do I need to buy a heater for my salt water while its mixing? Any answers are appreciated. Thank you.