you can switch salts mid stream, but it is better to do it slowly. do not do your biggest water change of the year using the new salt. if you do 10g a week. do 5g twice a week for a month than go back to your old WC schedule. this will help you to learn the differences in water composition for dosing.
Depending on how big your system is will depend on whether you go with RC or IO. If you have a really big system and you are savy with Calc and Alk, there might be no use getting the RC over the IO, as their biggest difference is the increase in CA. For most though the few bucks a month (or months) is not worth the savings in a reef tank. I'd recomend RC for most
I use Crystal Sea Marine mix. It is what my LFS has in stock. I was told that it is very good but I was also told that I could not change to another type of salt once I start using this salt. Am I doing something wrong here?
I was using Oceanic and had to switch to reef crystals because the oceanic caused my calcium to go through the roof. I also posted an add just like this and somewhere along the way someone told me I couldn't go from Oceanic to Tropic Marine several people said they had problems switching the 2.