When switching salts it's a good idea to gradually increase the amount of the new salt to the old so you don't shock the system. Ushually you are doing cups of salt to cups of salt, but since ESV is a whole system that you have to mix, I decided to mix what I considered 30G of RODI mixed with Tropic Marin to 10G of RODI with ESV. I just mixed it all in the same 45G tub. First filled tub with RODI--I estimated it to 40G RODI. Added heater and 1200 maxijet. Added 12C Tropic Marin salt and let sit for a few hours until I was sure that it was mixed into the water (no grains of salt left). Then added the ESV system by following the directions for 10G of water. I tested all parameters and they were all within good range. I didn't actually use the new water until the next day because of the Tropic Marin (like to wait 24 hours with that salt before using). I've been using Tropic Marin for several months and have had to add 2 part, bottles of Mag., and Alk powder to my tank to get the right parameters, but it's been a week since adding the new salt water mix to the tank and so far no need to dose. Huge difference. Loving the ESV. Really, you don't need to overthink this. Instructions are really clear. Mix the water and test it, if it's not correct, experiment until you get the right parameters. You are only mixing this in a tub, not your tank so just don't add it to your tank until you are happy with the results.