Yes if you switch salts you will shock your system and possibly lose all of your corals to a white out. If and when you do decide to switch. There are steps you have to take to do so. First when you are getting low on salt, this is when you can decide to switch. It has to be a slow switch done over the course of about 2 months. When mixing new water you should stay simple and start by adding around 10-20 percent new salt, withe the existing salt you are already using. This will allow your system to make a small change over to the new salt. Using just a lil more salt on each new water change until you have made it to the point where you are using only your new salt mix. You have to take it easy when switching salts. EXAMPLE>> Week 1 20% new salt/ 80% old, Week 3 40% new salt/ 60% old, Week 5 60% new salt/ 40% old, Week 7 80% new salt/ 20% old, Week 9 100% new salt. This will allow your system to adjust to the new salt, as well as give you time to see if there is any negative side affects that should have you go back to the original salt.