I started out in the hobby using Instant Ocean, but when I decided to go reef, I switched to Oceanic and never looked back. My calcium has been great and my corals and all the other tank mates love it...as do I. This is probably coincidental, but when I've had to use Instant Ocean in a pinch since switching, ummmm, I ended up with an algae bloom of one kind or another...again, could be coincidental. Oceanic is very easy to mix as well. Hope this helps.
Lisa