The debate between DIY live rock versus natural live rock often hinges on a question of ecological sustainability, which I find curious. Those who argue in favor of starting tanks exclusively with homemade “aragocrete” rock often argue that this material is more eco-friendly because it doesn’t come from the ocean. On its face, this seems plausible since homemade rock isn’t harvested from natural reefs, but looking a little deeper makes the issue a little less clear.
After all, the cement in homemade rock doesn’t simply come from the home improvement store; it has to be mined out of terrestrial limestone quarries (a finite resource), and put through industrial processes that undoubtedly consume energy and create pollution. All of the raw materials have to be shipped to your local store, including the thinning materials and reef substrate. Also factoring in the substantial amount of water required to “cure” homemade rock, it may not be quite as easy to weigh the ecological footprint of DIY rock versus natural rock.
By contrast, live rock that is harvested properly can be a more or less renewable resource; corals are constantly building new skeleton that inevitably forms new reef substrate. Additionally, it can be a significant source of revenue for the residents of developing island nations, who may be able to harvest live rock in place of a more destructive livelihood like overfishing the same reefs. While it’s not reasonable to suggest that our use of natural live rock isn’t a form of exploitation of the reefs, it probably isn’t such a clear choice whether homemade or natural rock is most sustainable. So pushing the sustainability question aside, what then are the advantages of each? And how should a responsible hobbyist decide how to create the perfect reef structure?
The advantages to natural live rock are what have kept it so popular over decades of reefkeeping. The natural diversity of tiny organisms that have the potential to colonize a sterile aquarium and create food chains for coral reef animals are only possible with the introduction of natural reef substrate such as live rock. While this can sometimes be accomplished by the addition of rocks associated with coral colonies, it is a necessary element of a modern reef system.
The advantages of DIY rock, on the other hand, largely parallel the disadvantages of natural rock. After all, homemade rock doesn’t carry the same potential for parasites or unwanted hitchhikers that natural rock does, nor does it harbor nuisance algae that might bloom in an unestablished tank. What I see as the primary advantage of DIY rock, however, is the fact that you can form it into literally any shape you can imagine. With the right technique and materials, it is possible to make a stable, proportional and attractive reefscape suited exactly to your tank.
So what is the best way to go? In my experience, nothing can replace natural live rock, but I have begun to think that homemade live rock definitely has a place in a system where you’re trying to achieve aesthetic perfection. As I set up my next reef tank in the coming year, I’ll definitely be using a combination of both natural and DIY rocks. And I expect that it will be my best tank yet!