Deltec Aqua Crown Hy Carb

Deltec Hy Carb is a phosphate-free, granular calcium reactor media specifically designed for use in Deltec fluidized bed calcium reactors. 

It's a pure, natural granulate that helps increase calcium and magnesium levels in marine aquariums. It's often used in conjunction with Deltec HyMag (a pure magnesium granulate) to achieve a desired magnesium concentration.