Allot of people use it in a sump for bio so it would work. It would look crazy though. Id say look at Texas holey rock or Florida limestone reef rock it you want a cheaper alternative to say pukani etc
Years ago on one of the national salt forums maybe reef to reef or reef central there was a guy who made a Hawaiian island tank he used lava rock and black sand and mangroves to build the island. It was really pretty cool. I just did a search and couldnt find it some like it probably copies but looked like they were using reef rock.