Epoxies won't hold weight until they have cured so if you are doing something funky or at an odd angle you'll need to prop the piece in place but other than that they work just fine. Shut the skimmer down though because they cause excessive foaming for about 24 hours.
I want to glue a purple gorgonian and a corky finger to a rock.Do I do it under water ? If not how long can the live rock and coral stay out of water ?
You can work with both out of water for a few minutes - the epoxy can cure underwtaer in fact it must you just mix the epoxy, knead it into a ball shape it around the gorg and into a rock crevice and place back into the water - propping the coral in place if necessary.
Z, I just used it yesterday to attach a pterogorgia sp. gorgonian to a angled piece of live rock. I am not a huge fan of it but for certain things it's the best especially for tall narrow corals - i.e. gorgonians. I found the best results are to be able to remove both the rock to be mounted to and the coral and pat each surface dry then put the epoxy on the rock then press the coral into it and form up around the sides.
I also was trying to use it to keep some of my plating montis to grow alond the back wall of my tank with little success.
My biggest complaint is to use enough to be effective you often end up with a big white glob that takes a while to cover with corraline.
Edit - here's what it looks like on my gorgonian. I had to prop a small piece of LR behind it to keep it in place while it hardens up some. I wanted this in a slightly higher flow area so we will see if the epoxy holds.
I like to use glue for my gorgonians. I drill a small hole in a live rock rubble. Then i strip back the flesh. Fill the hole with super glue and set the gorgonian. Hardens alot faster then epoxy and looks way better. If you want to put it on a rock in the tank, maybe do like i told you, then epoxy that piece of rock. HTH
Yeah what he said on the skimmer, if you forget your house is gonna STINK!! Your skimmer will start overskimming during the curing process and make a BIG mess.