i have a 240gal salt in my family room and since i set it up 5 years ago. I only use catalina water available at my lfs. I keep a nurse shark, a ray, lions, and groupers. Nurse sharks are very sensitive to their water and cant handle poor water quality at all. i have used synthetic salts and she was not happy. water quality is not an issue as long as you know where the water is coming from. also it helps to have a relative who works for a local city aquarium. He filled me in on who is the most reputable to deal with.