I just switched from I.O. to Reef Crystals (also made by Aquarium Systems/Marineland)
Everything is looking good so far.
I have not tested personally the other salt brands, but have heard pretty good customer feedback for OceanPure.
I did quite a bit of research on salts before switching from I.O. and talked to a lot of people. From what I gathered, many people have been very happy with both Reef Crystals and OceanPure.
OceanPure, however, is cheaper and easier to find around here.
Maybe I'll have to setup another little nano tank and give OceanPure a test run. Also have heard good things about Seachem's new Reef Salt. I would like to give that a test too.
Edited by lgreen