Reef Essential® Signature Series™ Rubidium is designed to provide ultra-pure Rubidium for Reef Aquariums. Rubidium is an essential element found in natural seawater, and in order to replicate natural seawater parameters as close as possible, supplementation is highly recommended. Recommended Rubidium concentration = 0.03-0.05ppm Suitable for these Saltwater environments: FOWLR | LPS | Mixed...