I recommend you dont use glue like this..... over time I believe the glue will unstick or possibly become very fragile/brittle over long term. Also if you plan on having coral on that rock could become a mini coral landslide if you were to bump it the wrong way while doing tank maint. Instead I would recommend you get one of these http://www.reefsupplies.ca/online-store/The-Rock-Mag-Junior-Magnetic-Rock.html or http://www.reefsupplies.ca/online-store/The-Rock-Mag-Magnetic-Rock.html depending on the size you need and use it as a anchor. Then use that faux rock and assuming you'd be gluing the liverock onto another rock already in the tank you would have a more solid & sturdy bond. My two cents im just thinking longterm plus murphy's law.