Got it out of Coral and Reef magazine. Buy White Portland cement, crushed puka shells, crushed coral and water softened salt.
2 parts crushed corals, 2 parts crushed puka shells, 1.3 parts white Portland cement. Mix with water so wet and holds shape. Kinda like oatmeal or granola. Mix in one part salt for porosity. Shape and left dry 48 hours.
Soak until ph is stable outside of display tank.
55 Gallon, DIY Live Rock, 2 Taotronics 130w LEDs, CPR HOB skimmer and refugium, 525 GPH SunSun 5-stage Canister with UV Sterilizer using Chemi-pure Elite, and Two Fishes GFO reactor and 3 800 GPH powerheads. <><