I don't see why the ivy wouldn't grow in coir. You could also try straight sphag or peat.

Now as far as ivy goes, in general, I find it to be more of a pain that it is worth. It is highly prone to spidermites, for me, when grown outside of a terr. Inside a terr, the constant high humidity could be problematic for it. If it does do well, then be prepared to prune regularly. Ivy can be a major thug in the great outdoors, I wouldn't be surprised if the same held true in a terr if it proves to like it there.

I am setting up terrarium to house hermit crabs. I am using a 10

Gal aquarium .I would like to use silica sand coco fiber. Instead of dirt. And I want to . Plant moss spider plant and Jews. Will this be possible and how should I mix coco fiber with sand or keep it desperate and do a half half set up.