Started with IO, and was given a bucket of Oceanic, so I switched, and was able to reduce my dosing with calcium quite substantially, but have since run out of Oceanic and gone back with IO. I read an article on the about forum that contained a poll of a few thousands of users, and IO was above and beyond the most used salt.......but why is anyones guess......is it because folks actually think its superior, is it because of the price is it because its virtually in every shop around....who knows. IIRC Tropic Marin was 2nd most used salt, and Oceanic brand was not even listed. The way I look at it is find a salt, and salt, try it and if it works for you use it.......IMHO except for trace elements and proportions of trace elements, its all suitable for a marine setup......so some may need additional supplements where others may not......