What kind of coral, and how did it happen? If it detached on its own, it should resettle, though maybe not where you what it to. If not, knowing what type of coral it is will help me to suggest a method of reattachment.
It's a mushroom coral that has grown to about 7 in. in diameter. I recently added a new power head and the coral is settled in the bottom of the tank (crushed coral). I'd like to reattach it to a better viewing spot in my tank (55 gal), or at least get it off the bottom.
Obviously it didn't like the water flow, they do like an area of lesser indirect flow BTW. Well one way is to get a piece of tulle fabric or wide ribbon...kinda like bridal veil or fine fishnet. You take the fabric and sort of net the coral, foot side down and place it onto the rock. You can tie the farbic around the rock (if the rock is small enough) or use straight pins to secure the net to the rock. You can try gluing it where you want it but the best way is to use the netting and let it settle on its own IME, I only superglued them as a last resort.
i use pantyhoes and put the rock and shroom inside, cut what i dont need, rubberband the end, then place in the tank..it works...looks a little wierd for a while but itll do the job. its fine as long as you dont get dark ones...(they diffuse the light alot...)