Brightwell Aquatics Magnesion-P - Dry Magnesium Supplement, 3.2 kg.

* High-purity powdered magnesium blend.
* Provides magnesium, which helps regulate the balance between calcium and carbonates in aquarium water, and is a component of aragonite, the mineral secreted by reef-building organisms to form skeletal material.
* Stronger and more economical than liquid magnesium solutions; created for hobbyists maintaining multiple reef aquaria.
* Formulated by a marine scientist.