I dont think they are the same. The IO is more of a All SW
salt while the Reef crystals is more of a formula to benefit corals, anenomes and other reef inhabitants. I dont use either one but this is what I have read. This is what IO says about them. There is a difference
Instant Ocean® sea salt contains every necessary major, minor, and trace element and has no nitrates and no phosphates. It was developed through sophisticated biological and chemical testing, and every batch is analyzed to assure consistent high quality. Exceptional solubility, uniform particle size, and outstanding package value have made Instant Ocean® salt the choice of aquarists for over 40 years. No other product outperforms Instant Ocean® salt. Our guarantee of quality is supported by a history of proven usage. Instant Ocean® is the world's most popular brand of sea salt. It is available in 5, 10, 25, 50, and 160 gallon sizes.
Reef Crystals® enriched blend sea salt
Reef Crystals® enriched blend sea salt contains extra levels of calcium, vitamins, and selected trace elements. Developed for use in sophisticated reef aquariums, it was the first enriched sea water formulation available to aquarium hobbyists. The inclusion of important components at concentrations greater than in natural seawater assures extended availability of substances that are assimilated and depleted especially quickly in thriving reef aquariums. A special additive helps to detoxify excess heavy metals, such as copper, that are often found at elevated levels in domestic water supplies. Reef Crystals® salt provides superior dissolvability and is compatible with all marine aquariums. We use only the most sophisticated biological and chemical test methods to develop and refine our formulas, and Reef Crystals® sea salt is no exception. Every batch is carefully analyzed to guarantee composition, consistency, and uniformity. Reef Crystals® is available in 10, 25, 50, and 160 gallon sizes.