At AquaCave, we offer some of the best selection & best prices on advanced salt mixes and refractometers for you marine and reef aquarium. Synthetic sea salt mixes offer a convenient, do-it-yourself way of creating saltwater for your aquarium. When mixed with RO/DI filtered tap water, synthetic sea salts become pure saltwater with consistent calcium, alkalinity and pH levels. And, thanks to the purity of the formulations, synthetic sea salts are nitrate and phosphate-free, minimizing the likelihood of unwanted algae blooms in your aquarium. Higher-priced salt mixes often contain higher calcium, alkalinity and trace element levels, which make them better suited for the reef aquarium environment.