Madeira is a vulcanic island so, yes, it's volcanic dead rock. I picked it up yesterday on the beach. But it's very pourous, so I guess that in time it will turn into good live rock.
I also have some bits of halymeda and some "sprouts" of xenia.
I don't want to put any fish inside. In a few months, just a shrimp (what do you think about a stenopus hispidus?) and a small cleaning crew.
To tell you the truth, I've never seen a photo of a marine planted tank. I'm going to take your hint and try to see how they look and work (I should have done this before).