@york1 has good advice, find the salt with the parameters you want. I make and mix my own saltwater now and recommend it, but I never had any issues with store bought water from my LFS for the first 6 months I had my tank. I bought premixed salt water at first, then RODI that I mixed with my own salt, Red Sea Coral Pro, and then got my own RODI unit that I upgraded a year later to 7 stage and moved to Tropic Marin Classic when I was ready to start dosing. BRS has a cost video, the good salts are all pretty close to each other in price. If you don't maintain your own RO/DI system after you purchase one, your water quality can drift so be diligent about it.