I think u got it the other way? RC is for reef... Blue one is for FOWLR?If I recall correctly, you want IO Instant Ocean (the purple one), not the IO Reef Crystals (the orange one).
I was told the Reef Crystals is for Fish Only tanks, while Instant Ocean is for marine/reef.
I use the Instant Ocean. Dr's Foster's and Smith usually has the best deal with free shipping.