Maybe they've reformulated the older product. What I do know about Kent salt is that it used to be packaged by Aquarium Systems, and Kent provided the proprietary compounds. Aquarium Systems made Instant Ocean.
In response to the popularity of Kent's premium salt, Aquarium Systems came up with Reef Crystals.
When Central Garden & Pet bought Kent and other entities, Aquarium Systems didn't package the Kent product anymore. And Aquarium Systems and other entities like Marineland/Perfecto are now owned by United Pet Group.
Central owns AGA/Aqueon, Kent, Coralife/ESU, Oceanic and a host of other pet-related companies.
UPG owns Marineland, Aquarium Systems, Tetra and other pet-related companies too.
I'm headed to a trade show next month - I'll see Central reps there - I'll ask them if it's a new formulation or if it's just new packaging. Like I said, the SKU (UPC) numbers are the same as the original Kent salt. The original Kent salt was a higher quality salt - more trace elements, etc., and more formulated to reefs.
Jenn