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Captive-Raised Live Rock

It seems that no one is addressing the significant fact that captive-raised live rock does not contain anywhere near the amount and variety of life as reef-collected rock.

By John Tullock

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All the discussion on captive-propagated saltwater fish and invertebrates in this column over the last few months has led one reader to write the following letter regarding captive-propagated live rock:

Q. I have seen several sources on the web promoting captive-raised live rock, and it seems that no one is addressing the significant fact that this source of rock does not contain anywhere near the amount and variety of life as reef-collected rock. Captive-propagated rock is only good as a source of nitrogen-fixing bacteria and some forms of encrusting coralline algae. If one is only interested in having rock for maintaining a bacterial filter, then any man-made, non-polluting source of rock with a large surface area would do. However, my only real interest in reef aquariums is in everything that is not coral (e.g., hydroids, bryozoans, worms, sponges, tunicates and so on). Where would I get such a wide variety of these interesting creatures if not from rock taken from the wild? Certainly, no one is offering these life-forms for sale on a regular basis, and captive-propagated rock has been practically sterilized in the mistaken idea that this is cured.

As Julian Sprung once noted, most reefkeepers nowadays are maintaining parking lots paved with encrusting purple coralline algae. This does not look anything like real live rock in the wild. Real live rock really should be alive with hundreds of varieties of life-forms. If you know of some method for raising fully alive live rock, perhaps you could detail this in a future column.

A. The problem with wild-harvested live rock is that curing is necessary due to the way the rock is handled by collectors and importers. As a rule, the rock remains in the box — wrapped in wet newspaper — from the time it is first packed by the collector until it reaches the local fish store or even sometimes the consumer. This results in the massive die-off of the organisms in which you are interested. Curing is merely a way to avoid this happening in the customer’s saltwater aquarium, creating a huge ammonia spike and releasing lots of organic matter because of the decay of the dead organisms on the rock.

Captive-propagated rock should be distinguished from cultivated rock. The former implies the rock is produced in an artificial system from dead rock, and indeed is unlikely to harbor much more than coralline algae and bacteria. As such, it will work for filtration purposes just fine, as you point out.

Cultivated rock results from placing dead rock in the ocean and waiting a year or two for it to become encrusted. Cultivated rock might be tough to distinguish from natural rock from the same area, except that there is a requirement that the dead rock be geologically distinctive to prevent “cheating” by producers.

Before the harvest of Florida rock was banned, Gulf collectors shipped a lot of attractive rock from the Tampa area. However, because of the ecological conditions in the central Gulf, these specimens often fare poorly in tropical reef aquariums.

If Indo-Pacific rock were collected with an eye toward its appearance and diversity of encrusting life, and then kept submerged and shipped with the same care that is given, for example, to a coral specimen, it should arrive at the local fish store more or less intact, and would probably be exactly what you are looking for. However, this would also mean that each piece would cost about the same as a similar-size piece of stony coral, say $50 for a 6-inch diameter specimen. I suspect most wholesalers realize the market for this live rock would be rather small — maybe just you and me.

Further complicating the live rock picture is the ecological impact of harvest, leading some countries to ban or regulate collecting. Most Indo-Pacific rock now comes from Fiji.

Harvest of live rock in Florida and Hawaii has been prohibited for several years. Florida has an active cultivation program, but I am unaware if a similar program exists in Hawaii. The state of Florida issues a license for an entrepreneur to place dead rock in, and subsequently remove encrusted rock from, a specific area of the sea bottom, sort of like an oil drilling lease. These operations extend southward from the Gulf of Mexico, which has wider temperature swings and a different fauna from the truly tropical waters of the Florida Keys, with a consequent variation in the types of organisms found on rock produced in different areas.

When I was teaching coral reef ecology in the early ’80s, beautiful live rock specimens could be picked up in boat slips, inlets and other sheltered waters along US-1 through the Keys. Colorful sponges, tunicates, green marine macroalgae, articulated coralline algae that looked like the support structure for some futuristic building painted lilac, and pale blue lacy bryozoan colonies dotted the surface of each chunk of Key Largo limestone. The sessile phyla were accompanied by transients ranging from Astraea snails and blue-legged hermit crabs, to slowly creeping, eerie green Tridachia sea slugs. In the nooks and crannies on and between the rocks, green Mithrax sculptus crabs patiently scraped, feeding on algal mats, not even stopping or seeming to notice when the rock was plucked from the sea. Sometimes, a sponge colony harbored a tiny bumblebee shrimp, black and yellow body stripes bold and glaring, obviously shouting a warning of some kind to its potential enemies, color so flamboyant it could hardly be camouflage. Brittle stars slithered from underneath almost every rock disturbed, from the spiny, brick red and chocolate brown Ophiocoma echinata, to the weird Ophionereis reticulata, favoring clumps of Halimeda algae and flashing with yellow green bioluminescence when disturbed. My students often selected the ecosystems in miniature of live rock as subject matter for their term papers.

It is growing increasingly difficult to find these natural live rock areas in the Keys. My favorite spot, separated from the road by a stretch of tangled mangroves, recorded in my worn old field notebook with the precise distance from the highway mile marker, no longer exists. It’s been “built out,” as the developers say, and nothing remains that is not man-made except the hard limestone shelf that winter seas used to chew up, slowly renewing the supply of rubble clinging to the shoreline, offering new territory for colonization by millions of larvae on the next incoming tide.

Other spots, where the Tridachia grazed on Caulerpa and then stretched out under the fierce sun to live for a time on chloroplasts commandeered from their food, now harbor mostly empty plastic bottles. An oily film, washed by torrential tropical rains from the asphalt deck, changes the color of the ocean as it laps against the pylons holding up the mightiest transoceanic bridge system in the world.

Under the old Seven-Mile Bridge, built at the beginning of the last century, automobile guard rails cobbled up from steel that once bore Henry Flagler’s steam engines deep into the wilderness — the old Pigeon Key marine lab is no more. Restored, the buildings where I lived and worked now house a museum dedicated to the men who braved unbelievable hardships to connect Key West to the mainland with a railroad.

I drive across the new, four-lane bridge, glancing to the north toward the familiar layout of “dorms” and “labs” now reflecting the sun painfully back into my eyes from their recent coats of white paint. I wonder if one of those railroad workers, a grown man when my grandfather was a teenager, sweating six days in Florida’s shimmering heat for a few dollars a week, I wonder if he ever, on his day off maybe squatted down at the edge of the sea and picked up a rock and marveled at the teeming life he beheld. I wonder if our great-grandchildren’s generation will have that opportunity?

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