Live Rock

Live Sand

Plenum Grid

Hypoxic Water Layer

Hypoxic Water Layer

Top left: the Nitrogen Cycle in a conventional marine aquarium — nitrate accumulates as the end product of waste conversion. Bottom left: a natural system with a Monaco-style plenum — denitrification yields elemental nitrogen.

smelly with an odor of putrefaction, is coated with slime. Mobile animal life either lies dead at the bottom of the box or struggles feebly to avail itself of whatever moisture and oxygen might yet remain.

Among the earliest discussions of reef tanks, George Smit's (1986) articles make repeated references to the use of live rock in creating the aquarium environment:

"I believe that most hobbyists would agree, however, that the picture of a complete 'miniature reef/ complete with living rock, thriving algal plants such as Caulerpa sp., invertebrates that do not just exist' for a short period of time, but actually grow and multiply, along with healthy specimens offish, would be the ideal goal to achieve. Yet how many aquarists are actually aware of the fact that live rock is not just a decorative alternative to coral skeletons, but as necessary to the long-term survival of the miniature reef as the correct quantity and quality of light?"

Smit recognized the value of microorganisms associated with live rock and suggests, in the caption of one of the illustrations that accompany his articles, that live rock bacteria may even produce antibiotic substances with beneficial effects. He describes carefully how live rock may be used to "seed" the system with nitrifying bacteria. It apparently never occurred to Smit that live rock could be used to filter the aquarium all by itself. Perhaps this was because his primary focus was on the wet/dry filter system that he was introducing to American hobbyists. It was perhaps from Smit's writings that the notion of "seeded" live rock came to exist. The word "seeded," if used to mean cleaned and held after collection, is inappropriate and misleading in this context. It suggests that the rock begins its development

Chapter Three 85

Caulerpa Palythoa

Encrusted with coralline algae and calcareous macroalgae, Caribbean live rock can be exceedingly colorful.

A section of premium Pacific zoanthid rock from Fiji, covered with Palythoa polyps and a sprig of Caulerpa racemosa.

during the handling it receives before being put to its final use in a reef tank. It is more correct to say that the rock must "cure," or complete its development (like prosciutto or Stilton) after its having been "seeded" by nature. To appreciate the process of curing live rock and the effect this has on the aquarium environment, it is necessary to understand how this material reaches the aquarium marketplace.

Before restrictions were placed on the collecting of l ive rock in Florida, collectors might take specimens in only a few inches of water, just below the low-tide mark. At the extreme, road fill, barely wetted with each turn of the tide, but harboring a few tree oysters and blobs of filamentous algae, was boxed up and shipped to unsuspecting aquarists. As the unhappy recipient of one of these shipments, I cautioned employees not to cut themselves hauling the rock to the dumpster. I had visited spots in the Keys where rocks like this could be found, filthy coves where Styrofoam cups and broken glass were the most common species; I was concerned about the potential for infection.

Aquaculture efforts in Florida are placing substrate rock at depths ranging from 10 to 110 feet (Frakes, 1995). In the Indo-Pacific, rock is harvested at shallower depths, in part because collectors often lack equipment. In any case, collectors bring in as many chunks of rock as they can carry, and store them in tubs or baskets on the deck of the dive boat. Ideally, the rock is kept covered by wet blankets or tarps to prevent drying under the harsh tropical sun. W hen the boat returns from a collecting excursion, the rock is packed in boxes, usually surrounded by wet newspaper, and shipped via air freight to the dealer. This may be a retailer, as is often the case with rock collected in Florida and shipped to a store east of the Mississippi. If the rock originates in the Indo-Pacific, it will first arrive in the hands of a broker who takes care of the import paperwork bef ore shipping the rock along to the retailer. If the retailer is only able to purchase a small quantity of rock, another middleman, a wholesaler who supplies many dealers with both rock and other specimens, will be part of the picture. Along the way, the rock remains in the original packing container, so much depends upon how expeditiously the journey from some tiny island

15,000 miles out in the Pacific to the retailers holding tanks can be completed. Variations in transit time can have pro-

86 Natural Reef Aquariums found effects on the survival of organisms associated with of the dead organisms begins. The decay process releases the rock, in particular larger encrusting species like sponges ammonia and organic matter. Shiny, white growths of bac-or embedded mollusks. As common sense suggests, the teria and fungi spread over the dead areas of the rock. Decay longer the rock is out of the water, the fewer survivors.

Live rock may also vary as to bacteria produce hydrogen sulfide, which escapes from the tank and fills the air with the

the geological nature of the rock itself, the depth from which it is collected, prevailing water conditions at the time of collection, and the care (or lack thereof) with which the collector chooses specimens. The types of encrusting organisms will vary between two pieces of rock collected in different geographic localities or even be- Florida aquacultured rock with healthy Chicken tween one piece of rock and Liver Sponge, corallines, and calcareous algae, another collected a few feet away. Individual pieces can be slablike or flattened, rounded or gnarled, tremendously irregular, or even delicate and branching, such as the arms of staghorn corals that have died and been encrusted with coralline algae and other organisms. The best live rock is porous, with numer- Gulf of Mexico plant rock with an attractive shape ous holes and cavities that harbor not only small invertebrates,

Gulf Decorative Live Rock

and vibrant coverage by Caulerpa peltata.

pervasive smell of rotten eggs.

Real rotten-egg fumes are easy to take, by the way, once you have experienced the odor of decaying sponge. A high proportion of Florida rock used to sport numerous viscid colonies of Chicken Liver Sponge (Chondrilla) and sometimes other inshore species, even an occasional small Black Loggerhead Sponge (Spheciospongia vesparia). None of these survive well out of water, and most have already begun to decay when the rock arrives at its destination. Because sponges smell truly vile as they rot, I taught everyone at my company how to recognize and remove the offending poriferans as the live rock was unpacked. These were accumulated in a bucket and discarded. Unpacking rock can be tedious, algae, larvae, and spores, but also beneficial microorganisms. and as with any repetitive task, habit guides one's move-

Many such organisms are, surprisingly, able to survive ments while one's thoughts are elsewhere occupied. Some-

the shipping process. Others, however, are not so hardy. one once absentmindedly stuffed a bunch of dirty towels

This latter group, which includes various species of sponges, into the top of the sponge bucket, and the contents sat for cannot endure the rigors of travel and exposure to air, and several days at room temperature in the rear of the store, they perish. The die-off of these organisms has several ef- When the towels were removed for laundering, uncorking, fects when the rock is once again placed in water and decay as it were, the genie trapped below, he emerged a very an-

Chapter Three 87

noyed genie, indeed. "That smell," someone quipped, there for an additional week or more. The end result is clean

"would drive the maggots out of a dead mule s carcass."

rock with desirable marine life still intact, but without dead

"Curing" live rock simply involves allowing the die-off or dying organisms that would pollute a tank. If the rock and decay process to occur under controlled conditions, reaches us in very good condition, it may be completely cured in as little as a week, but more often two weeks are re-

Curing Dry Rock For Reef Tank

rather than having it take place in a display tank, where the consequences for the other inhabitants would be serious indeed. The occurrence of the die-off process led early authors on the subject of reef tanks to recommend placing all of the rock, which to these authors was only available uncured, into the tank at the same time, and waiting for Branching coral skeletons are typical of much several weeks before continuing Pacific rock, such as this fine Samoan example with the establishment of the reef community. With cured rock, this is no longer necessary, and the rock can be added in small increments, along with other organisms. Cured rock may thus be added in any amount, at any time, since it will not produce pollutants that can harm specimens already present.

Aquatic Specialists devel- Spectacular flattish rock from Panama, with oped its own method for curing corallines and various macroalgae species, live rock. Freshly collected rock

Reef Aquarium Macro Algae Identification

quired. If the rock has had a long or eventful journey, it may take a bit longer than three weeks. Cured rock has an unmistakable clean ocean smell, with no scent of decay. The sniff test is a reliable way to assess its condition.

Live rock is used to construct the support structure in a marine tank, forming a "reef" for the corals and other invertebrates that will later be added. The larval forms of invertebrates and algae that will eventually make their appearance on the rock give the aquarium a desirable natural look.

There are several specialty categories of live rock offered by some suppliers for aquarium decorating. These include: plant rock, mushroom polyp rock, zoanthid rock, and Christmas is first rinsed in seawater to dislodge sediment, and any ob- Tree Worm rock. For the organisms present on such live viously dead or dying organisms are removed. The rock is rocks to survive until used in an aquarium, the specimens placed in holding vats for a period of one week. At the end must be kept in water from the time they are collected un-

of that time, areas of decay will be apparent, and large de- til they reach their final destination. These obviously cost cay spots are siphoned off, or removed with a brush. After more to handle and ship and command premium prices.

another rinsing in seawater, the rock specimens are then

Some types of rock from the Florida area are becoming transferred to a second group of holding vats and are held less and less readily available, owing to collecting restric-

88 Natural Reef Aquariums tions. At the time of this writing, as I understand the situation, live rock harvest in Florida has been phased out completely (as of January 1, 1997, collection of any type of live rock product was banned). Thus, rock colonized with Florida False Coral (Ricordeaflorida) is now seldom available, although these specimens were once quite common. The Green Sea Mat (Zoanthus sociatus), and other species of sea mats, as well, are now seldom seen in Florida collections. Cultivated, or farmed, rock is likely to be the only Florida live rock available, and this will consist of coral rubble or rock collected from land and deposited in aquaculture zones to be colonized by marine algae, organisms, and bacteria. The Indo-Pacific remains the primary source for specimens of mushroom polyps, sea mats, and other assorted cnidarians that are supplied as colonies attached to a chunk of rock. Rocks such as these are often adorned with brightly colored sponge colonies, macroal-gae, assorted fanworms, tunicates, and other small organisms, in addition to the dominant invertebrates.

Types of Live Rock

PLANT ROCK is simply live rock upon which one or more species of macroalgae predominate. There may, of course, be additional organisms present on the rock, but plants are the primary colonizers. Such material generally does not come from the reef itself. While certain macroalgae are found on reefs, plant rock is most often collected in shallow, back-reef areas, where the absence of herbivorous fishes permits many types of seaweeds to flourish. Macroalgae add a desirable, natural appearance to the aquarium. Introducing macroalgae via plant rock is one of the best ways to establish these species in the aquarium. Some very beautiful specimens once came from the Florida Keys. Plant rock is sometimes available with healthy growths of species such as Dictyosphaerium, Valonia, or Codium present. More often, however, only Caulerpa, a more widespread genus, is present. Calcareous macroalgae such as Udo tea, Penicillus, and Halimeda often do best if obtained attached to plant rock. Many other species of macroalgae may be found on plant rock, and these may vary considerably in their adaptability to the aquarium. The aquarist can spend many fascinating hours in establishing a tank devoted primarily to macroalgae, and such a project is to be encouraged. A macroalgae tank can contain many organisms besides the algae themselves: seahorses, slugs, and certain anemones that are found in heavily vegetated shallow-water habitats. ZOANTHID ROCK comes from both Atlantic and Pacific sources. This material, mostly collected from shallow water, is dominated by the presence of one or (rarely) more than one species of zoanthid, or "sea mat." By far the most commonly available specimens once were colonies of the Green Sea Mat, Zoanthus sociatus, from Florida and the Caribbean. Less commonly seen were the golden sea mats, Palytboa sp. and Isaurus duchassaingi, a related species. From Hawaii, seven species of sea mats were once available. The most attractive is Isaurus elongatus with polyps about 2 inches in length. In Isaurus, the dime-sized crown of tentacles is usually a lovely greenish blue color. Palythoa vestitus, P. psammophilia, P toxica, Zoanthus pacificus, and Z.

Pigmentation Palythoa

Well-established zoanthid rock, almost completely covered with a green sea mat, Zoanthus sp.

Chapter Three 89

Nitrate Rock Are FoundZoanthid Hawaii

kealakekuanensis are also found on Hawaiian live rock spec- men, the greater the likelihood that it came from shallow imens. While these specimens are no longer collected in water. Ricordea needs plenty of light. With the closure of the Florida or Hawaii, similar species may be found on speci- Florida Keys to all live rock harvest at the end of 1995, false mens from other localities in

as much silt as possible before being exhibited. Other zoan- Brazilian rock, displaying an appealing irregular thids, including Palythoa carib- shape and good coralline growths.

aeorum, P. tuberculosa, "Para-zoanthusgracilis" (not a true scientific name), and P swifti, are deep-reef organisms and thus are not found on sea mat rock from shallow water. These species also make good aquarium inhabitants. FLORIDA FALSE CORAL (.Ricordea florida) is a favorite species of mine. Like the mushroom polyps imported from the Aquacultured Florida rock with macroalgae and small Pacific, Ricordea polyps are flat- colonies of stony corals, tened disks, averaging about an inch in diameter, that occur in scattered colonies in waters up to 60 feet down. The tentacles are round knobs about coral rock is now seldom available, but if one can locate a specimen, it makes a striking addition to the aquarium. Like all mushroom polyps, it is easy to keep. Mushroom polyp rocks from the Indo-Pacific are readily available and make fine aquarium specimens. They propagate themselves easily under good conditions. BASE ROCK is a term used to denote material that is mostly devoid of living organisms. This stuff tends toward heavy, rounded pieces that are neither attractive nor particularly easy to stack to create an open framework. Advances in the production of aquacultured live rock, using porous artificial substrates, together with the ban on collection of Florida live rock, will probably eliminate "base rock" from the aquarium trade. Good riddance, in my view.

Organisms on Live Rock

Viô-inch across and are usually bright blue-green in color, al- The variety of life present on a live rock specimen, though specimens are rarely orange, pink or blue-gray in and the state of health of that life, turns upon one important color. The more green pigment present in a given speci- issue: was the rock collected, packed, and shipped without

90 Natural Ruf Aquariums prolonged exposure to the air? In other words, was each individual piece handled separately and treated like a shrimp or fish specimen, or was the rock harvested in bulk and shipped "dry," i.e., covered with wet newspaper? "Dry" shipment results in rock that has to be cured before it can be used in the tank, as a result of significant die-off of the fauna on the rock. I have discussed the curing process in detail above. Cured live rock is therefore not heavily encrusted with a multitude of life forms. These may appear later, though, after the rock has been in an aquarium for several months. By contrast, live rock that has been kept submerged often has no die-off at all. As a result, delicate species like sponges and tunicates survive to become part of the aquarium fauna. Such rock needs no curing.

One frequently seen type of live rock deserves special consideration. Rocks from the Gulf of Mexico, harboring colonies of the serpulid annelid Spirobranchus giganteus, the Christmas Tree Worm, are regularly seen in the aquarium trade because of their multicolored beauty. While these specimens are not appropriate subjects for the tropical reef aquarium, they do deserve the interest of aquarists who might create a tank focused upon their unique habitat (see Chapter Seven).

The fact that highly successful reef systems can be created using live rock as the sole source of biological nitrification and denitrification — Berlin-style reef aquariums — is strong evidence for the important role of live rock mi-crofauna and flora. Julian Sprung has suggested to me that biological denitrification occurring within anaerobic areas of live rock removes nitrates from the system as they are produced, with little or no accumulation in the tank. My own observations support Sprung's contention. One aquarium of mine in particular never had a measurable level of nitrate in three years' time, despite a typical "load" of invertebrates and fishes.

What role, if any, other live rock organisms may play in the ecology of the aquarium has yet to be determined. One can suggest several possible benefits, however, from rock that has a full, natural complement of life forms present. First, the encrusting fauna of live rock assist in nutrient management in the aquarium by sequestering nutrients within biomass rather than having these same compounds available as particulate or dissolved substances in the water. Second, many of these organisms aid in detritus removal. Certain worms, for example, accumulate little piles of debris near the holes in which they live, facilitating its removal by the hobbyist. This represents another form of nutrient management. A third possible benefit is the production, almost continuously in some species, of larvae that constitute the tank's "plankton." A fourth benefit, less tangible than the others, is the inherent stability created in a system that is highly diverse. It is an axiom of ecology that very diverse ecosystems are better able to weather stress than simpler ones. While the typical tank may contain 30 or 40 species of algae, invertebrates, and fishes, the number of species on a single piece of live rock, when all the bacteria, protozoa, and microinvertebrates are counted, can number in the hundreds. The live rock fauna thus contributes significantly to the biodiversity of the aquarium. From the foregoing, it would seem obvious that one wants live rock with as many organisms as possible present. However, there is a catch. Preserving the maximum number of species requires that the rock be kept in water during the journey from the point of collection to the aquarium, as mentioned before. I have verified this observation repeatedly on collecting excursions. Air freight is a big part of the cost of live rock, and shipping the rock in water will add significantly to its weight. Because the cost of air freight is determined by weight, rock shipped in water will ultimately be much more expensive to the consumer than rock shipped "dry." Thus, the choice, as usual, becomes one of ecology versus economy.

What about my contention that Florida "base rock" is

Chapter Three 91

not as useful as live rock from the Pacific? My thinking re- for live rock that is highly branched, porous, and free of suits from two sets of observations. The first of these I call embedded boring sponge growth. Generally speaking, these the "boring sponge" argument. Certain sponges, chiefly traits are the ones consistently found in rock imported from species of Cltona, actually bore into carbonate rocks and the Western Pacific, from locations such as the Marshall infiltrate the rock mass with their bodies. This infiltration Islands. Porous, attractive rock is being aquacultured in large can be very extensive, with perhaps 25% of the rock replaced quantities on the Gulf side of Florida, and new sources of by sponge tissue. Like most other sponges, Cliona tends to wild rock from Panama, Central America, and Brazil are die when removed from the water. The dead sponge decays also emerging. (The last year for any wild live rock collect-very slowly, and the resultant pollution is produced over a ing in the waters off the United States was 1996.) very long period of time. When this happens, the rock frequently sports a growth of filamentous algae that is virtually impossible to control. This scenario might explain why, in an otherwise pristine tank, one tenacious patch of algae defies all attempts at eradication.

The other argument I call the "shape" argument. Consider first that the primary object in using live rock is to aid in nutrient management in the tank. Remember that nitrification, an aerobic process, occurs on the surface of the rock, and den-itrification, an anaerobic process, occurs in the interior of the rock. This arrangement facilitates Gulf of Mexico rock with hangers-on: Murex snail, limpets, sea cucum-coordination of these two processes, as envisioned ber, Clinging Crab, urchin, and tiny brain corals (at right), by Sprung. If these assumptions are correct, pro

Live Rock Coral

cessing of nitrogen compounds from the water will occur

Some of the organisms on live rock belong to taxonomic most efficiently when exposure of the water to rock surface groups encountered nowhere else in the aquarium trade. I

is at maximum. So a rock that is branched and porous, with shall briefly mention each of these minor groups here, since lots of crannies, crevices, and holes, is more desirable than many aquarists want to know what is inhabiting their live a rock that is relatively solid and shaped like a brick or rock specimens.

rounded lump. This is the same reasoning that is applied SPONGES are often imported for the aquarium and may to the selection of plastic widgets for filling the biological do very well in the reef tank. Live rock specimens may har-

chamber of a trickle filter. Rather than using Ping-Pong bor a variety of sponges in an array of colors. Sponges can be balls, trickle filters employ a variety of spiked, perforated, distinguished from the remainder of the organisms listed and ornamented doodads in an effort to provide the maxi- by virtue of their porous structure and the absence of ten-

mum amount of surface area for bacterial colonization.

tacles of any kind. As mentioned earlier, beware of fouling

By these two arguments, then, the optimum choice is from sponges that have been exposed to the air.

92 Natural Reef Aquariums

Astrangia SolitariaLive Rock Caribbean

Fanworms on coral-encrusted rock in the Caribbean: many such organisms can emerge from high-quality live rock.

Fan bryozoans and Encrusting Red Sponge in Biscayne Bay: Florida rock now comes only from licensed aquaculture sites

ANNELIDS AND OTHER WORMS. In addition to embedded fanworms of various types, the fauna of live rock may include cirratulids — a family of annelids with long, spaghetti-like tentacles. A bewildering variety of motile annelids with scales, spines, and bristles may disclose themselves once the rock is in your tank. Only large or numerous bristleworms pose any threat of harm to other reef tank organisms, however. Minor worm groups, usually found within the rock's crevices, include sipunculids, also called peanut-worms, and the rare echiurids. Sipunculids are usually drab in color and have a long, extensible proboscis. Echiurids are often brown or gray, but occasionally are lavender, pale green, or other pastel shades and may be distinguished by a flattened, triangular proboscis. Sipunculids and echiurids are detritus feeders. I have often found sipunculids as a result of the breakage of a piece of live rock. At Aquatic Specialists, it has become routine to feed dying invertebrates found in rock shipments to the fish. When an employee recently did feed a little brown sipunculid from a shipment of Tongan live rock to a mixed tank of fish, the results were quite unexpected. Only two fish in the tank nibbled at the worm, and both were rapidly and dramatically affected. Coloration became pale, and overnight the fish exhibited signs of extreme dehydration. Dehydration probably occurs as a result of kidney failure, and the resulting emaciation of the fish happens rapidly. The fish are literally "pickled" by the salty water surrounding them. A common feature of toxic reactions in higher vertebrates is the shut down of renal function. If these observations indicate that the skin slime of the sipunculid is toxic to fishes, the toxin must be a potent one. No damage at all could be found on the worm, meaning that none of its flesh was tasted by the fish. Thus, only a minute amount of secreted material induced the effects, and no other fish in the same aquarium was affected in any noticeable way. After about two days, during which they hid and refused to eat, the two affected fish emerged from hiding, apparently good as new. Moral: feed not that which you do not know for sure is safe! Sipunculids are rarely seen outside their retreats in the rocks, but apparently when they do venture forth, they do so well armed in the face of danger from predatory fishes.

Nemertean worms are flattened, ribbonlike, and very

Chapter Three 93

elongated. They may be variously colored and patterned. the size of a grape or marble, can clearly be seen to possess

Nemerteans feed on small invertebrates, but pose no threat a pair of body openings, side-by-side. Water is drawn into to the inhabitants of the reef tank. Flatworms may also be one of these, the food material is strained out, and the wa-

quite colorful and can be recognized by their smooth, very ter is expelled through the other opening.

flattened bodies. They are seldom more than an inch or two

Regardless of its source or the nature of the organisms in length. Most flatworms are predatory and feed on other attached, live rock is an essential component of the natural invertebrates. If you find one, observe it closely to determine marine aquarium. I compare live rock to the soil in a fertile its feeding preferences; remove it from the tank only if it garden because of its significance to the living processes tak-

seems to have a taste for something you plan to protect.

ing place within the captive ecosystem. Most important

Live Sand

BRYOZOANS. The bryozoans are all colonial, and many among these processes are nitrification and denitrification, resemble plants. In fact, the name "bryozoan" means 'moss which are both mediated by bacteria, animal." These are filter feeders that may encrust large areas of live rock, forming colonies that are often rather stiff and hard, owing to a skeletal structure composed of calcium carbonate or tough protein material. They can be recognized The Monaco-style aquarium is analogous to the by a circle of tentacles that is just visible to the naked eye and Berlin-style in that it relies on natural, bacteriological appears much like a tiny fanworm. Most are quite colorful. processes occurring within the aquarium. Dr. Jean Jaubert of

TUN I GATES. Many species of colonial tunicates may be Monaco has exploited this approach using the natural prop-

found on live rock specimens. They are beautiful animals, erties of reef sand to create inexpensive, effective filtration usually colorful and quite delicate-looking, appearing to be for reef aquariums. Jaubert s methods were described for the constructed of translucent glass. Larger tunicates, about benefit of American hobbyists by Sprung and Delbeek

Hawaiian Glass TunicatesDwarf Cup Coral

Often overlooked, delicate tunicates are relatively common on live rock that is shipped with care and kept in good water.

Dwarf Cup Coral, Astrangia solitaria, a hardy stony coral frequently seen on rock from Florida and the Caribbean.

94 Natural Reef Aquariums

Establishing a Monaco-Style System

(1990) and by Frakes (1993a, 1994). In brief, this technique relies upon a thick layer of sand on the aquarium bottom to provide an appropriate home for denitrifying bacteria. Ei- For tanks of up to 200 gallons, here is a step-by-

ther a bed of live reef sand or, more commonly, a layer of step explanation for establishing a Monaco-style system:

aragonite sand seeded with a quantity of live sand collected

1. A false bottom of plastic light-diffuser grid, called from the ocean floor is used. Small organisms present in eggcrate, is suspended about 1 inch off the bottom of the the live sand help keep the substrate biologically active, aquarium tank. The plastic must cover the entire bottom se-

while denitrifying bacteria thrive in the low-to-zero oxy- curely and should be made in two pieces to facilitate instal-

gen conditions in the deepest layer of the sand. This tech- lation. Straight couplings for %-inch (ID) PVC pipe, which nique results in denitrification, and the dissolution of the are about 1 inch in outside diameter, can be used to sup-

aragonite returns both calcium and carbonate ions to the port the plastic grid. Place each coupling on its side and water. Dr. Jaubert has been successful in maintaining high secure it to the grid with plastic cable ties. Use about one levels of calcium and alkalinity in his systems, together with coupling every 6 inches in each direction to be sure of ade-

low levels of phosphate and nitrate, through reliance on quate support. Off-the-shelf grid systems are also avail-

these natural processes alone. The tremendous surface area able, including undergravel filter plates available from any within the sand bed apparently adds significantly to the bi- aquarium shop. Simply remove and cap the lift tubes to ological filtration capabilities of a captive system, and many create an enclosed plenum under the sand. Other commer-

reef aquarists who have augmented their former Berlin-type cial models, such as the Eco-Sand Filter Plate (shown on systems have reported better nitrate control and increased facing page), provide further options.

coral growth with live sand and live rock, rather than with live rock alone.

Good Growth Live Rock Plenum System Reef Tanks

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Plenum System Reef TanksDirty Coral Reef Plenum System Reef Tanks
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