[Arklier]

Great Stuff is a sealant used for stuffing up cracks and holes in houses. So it has to be waterproof. People use it for drip walls and stuff like that, so I doubt it will effect the water in any way.

As for silicone, just make sure you get 100% silicone. They sell stuff specifically meant for aquariums at the pet store, but it comes in tiny tubes that are hard to work with, and it costs an arm and a leg. You can find aquarium grade silicone in caulking tubes at http://www.fantasticfrogs.com. Or just do what I did and buy normal 100% silicone caulk at the hardware store. It was only $6 for the tube. While it says it's not for aquariums, I don't see how that could be possible if it really is 100% silicone, so take that with a grain of salt.

 

[Arklier]

GE Silicone II is what I was referring to in my post. It's great, and much cheaper than the specialty aquarium caulk. Then again, I'm not caulking aquariums. I use it for sticking stuff to the walls of the aquaurium, not sealing it. If I were actually building a viv from scratch, then I'd go with the specialty stuff.

Anyway, as for Great Stuff, I've worked with that too. It is very difficult to shape, because it's extremely sticky. Even when it just comes out it's got the texture of warm chewing gum. My suggestion would be to get some large tongue depressers from the drugstore or something else disposable to shape it as best as possible. You will not need silicone to coat it, as the surface is very tacky for quite awhile. Shape it, then sprinkle dried Bed-A-Beast or other coir product directly over it. Black Jungle has a tutorial on their web site showing how to do it.

 

[Arklier]

Arklier have you skiped the silicone step and aplied the coco bedding right to the great stuff, Or do you know people who have? And how did it work?

I haven't personally used it for a whole background. I've used it to stuff cracks in tree fern panel backgrounds, and sprinkle coco bedding over it.