I'm using Instant Ocean, but I know a guy going to school to be a marine biologist who also does home reef tanks. In one of his classes they were taught that Instant Ocean salt adds phosphates to the water, even though the packaging says it doesn't. They tested, and sure enough, phosphates were detected. He recommended Oceanic brand, which is actually a little less expensive anyway. Needless to say, when my current stock of IO salt runs out, I'll be using Oceanic.