RHINO SKIN Tough Skin Protects Give your plants Rhino Skin to increase the rigidity of the cell walls making your plants' stalks more rigid. Plants take silicon into their cells making tougher cell walls. Rhino Skin is specially designed for use with all hydroponic growing media, including coco coir, as well as continuous liquid-feed growing systems such as aeroponics, drip irrigation and emitters, NFT, flood and drain, and deep water culture.