As with the stony corals, fusing of the rocks by coralline algae is a slow process. Coralline algae are considered the natural cement of the reefs, though truly their work is much assisted by the faster growing sponges that fuse the rocks and sediments together, in turn becoming covered by a veneer of coralline algae. Many coralline algae will form fast growing circular crusts on surfaces within the aquarium, but a few types, such as Mesopbyllum, will actually form attachments between rocks.
Plating growth of coralline algae (Mesophyllum) in a 10 year old Dutch reef aquarium. J.C. Delbeek t
A minor sort of attachment occurs where the byssus filaments of clams are adhered to several rocks. This effectively holds the rocks in position.
Sometimes people think that adding coral sand to their reef tank is taboo. This notion is probably partly owing to old recommendations in aquarium literature that said, in effect, that a sand or gravel bed without an undergravel filter to pull water through it would become foul and release toxic hydrogen sulfide into the water. In more recent recommendations in North American reef aquarium literature, sand or gravel on the bottom has been discouraged because it is perceived as a detritus trap that can promote the proliferation of undesirable algae. These partly factual notions have resulted in an unfortunate proliferation of tanks with nothing at all on the bottom! We hope we can change that trend with our recommendations in this book.
The "bare-bottom" idea affords a good measure of the detritus production by the rocks, usually an awful lot, and it is easy to siphon this away or prevent its accumulation with bottom water jets. Such an arrangement certainly prevents the accumulation of detritus, but it does not make for a natural aquarium ecosystem.
Sand has some important functions in the reef aquarium. It is decorative, of course, affording a realistic appearance and a complimentary, lighter colored horizontal contrast to the upright structure of the reef. Beyond that, sand serves some wonderful biological functions that can be used to advantage in closed system aquariums, provided simple rules are followed.
The rules include using Sleeper Gobies (Valenciennea spp.), sea cucumbers and possibly small pistol shrimps (for large aquariums only since they can bother fish in small aquariums), to maintain the substrate. Goatfish are also good at stirring up the bottom, as are a number of the small Partner or Watchman gobies (Amblyeleotris spp., Amblygobiusspp., and Cryptocentrus spp.), Pholidicbthys leucotaenia, and Istigobius spp. gobies (see Delbeek and Michael, 1993). Certain polychaete worms and serpent stars also help keep the sand clean, and they are generally introduced to the aquarium with live rock. All of these organisms constantly sift the sand in search of food or in the construction of burrows, thus aiming it over and preventing algae from coating the surface. This action also prevents detritus accumulation and the formation of dead spots.
Valenciennea puellaris. J.C. Delbeek.
A mated pair of Valenciennea strigatus. J.C. Delbeek.
Valenciennea wardi. J.C. Delbeek.
Istigobius ornatus. J.C. Delbeek.
Cryptocentrus cinctus. J.C. Delbeek.
Pholidichthys leucotaenia is a strange, eel-like fish that digs burrows in the sand, excavating and aerating the zones beneath rocks. J. Sprung and J.C. Delbeek.
Note: The gobies can only sift fine sand, as gravel may injure their gills. The sand should not be powder fine, but coarse, about the size of sugar crystals or a little larger. The most desirable and natural looking material is real coral sand, which is collected from o beaches in the vicinity of coral reefs. A few coral fragments or small stones thrown in provide a natural appearance as well as useful building material for fortification of burrows. Pet dealers should be able to obtain coral sand for vou from a number of
different suppliers, though it may become scarce in the future as a result of restrictions on the importation of coral.
A goldenheaded sleeper goby sifts sand through its gills. J. Sprung.
A small sea cucumber, Holothuria sp. feeds on detritus by mopping up sand. J. Sprung.
Certain Holothuria spp. sea cucumbers which resemble turds (yes, we said that) are also desirable for keeping the sand clean. As they move through the sand, they ingest it and digest any algae, detritus
and bacteria attached, which provide them with nutrition. Their digestive acids even liberate a tiny amount of calcium to the water.
Sea cucumbers are really best at mopping up detritus from between grains of gravel. Beware! avoid large sea cucumbers (greater than 15 cm; 6 in.) and never include a "Medusa Worm" (Synapta sp. sea cucumber) in your aquarium. Synapta sp. are toxic to fish when injured, and large sea cucumbers also can poison an aquarium if they become injured or suctioned by a powerhead. Small sea cucumbers present no danger. The colorful Sea Apples (Pseudocolochirus sp.) and other species that are just filter feeders, are best maintained by themselves as an exhibit, as they too can be toxic to fish when injured, and their eggs are so poisonous that they are deadly candy for the fish that eat them.
The benefits derived from sand are its effect on water quality and the refuge it presents to microorganisms, worms and crustaceans (see chapter 5). When the sand is thick enough, 2.5 cm (1.0 inch) or more, anoxic zones develop adjacent to aerobic ones, and biological processes occur as in live rock but more efficiently. The bacteria that colonize the sand denitrify the water. The bottom substrate is a most efficient, built-in denitrifying filter! Though some people prefer to maintain thin layers of sand, there isn't a limit to its acceptable, safe depth. The thicker it is the greater potential there is for denitrification. One must remember, though, that a living sand bed consumes a lot of oxygen. As long as there is strong circulation within the aquarium, the aerobic sand layer on top is maintained, and the aquarium will remain healthy. 71 le microorganisms, worms, and crustaceans living in the sand also digest detritus settling there, and their reproduction in this refuge generates food for the filter feeders and fish. Additionally, the digestion of detritus liberates carbon as food for the facultative anaerobic bacteria in the sand, fueling the denitrification process.
Some aquarists like the look of gravel on the bottom of the reef tank, but gravel is a little more difficult to maintain than sand. The same is true of coral fragments or small live rocks on the bottom, which are effectively big gravel. The depth of the gravel bed is not critical, though thin layers are easily serviced by manually stirring them. When the bed is thicker than about 2 cm (0.8 in.), certain creatures play a key role in its successful maintenance. Fortunately there are some natural cleaners that can be employed to keep the gravel bed healthy. The small sea cucumbers mentioned earlier are useful for this purpose, but Sleeper gobies cannot help here. Another useful creature is a small, harmless type of bristleworm
(about 5 cm (2 in.) or less and as thick as spaghetti) that multiplies prolifically in the gravel. It resembles the undesirable Hermodice caruncidata that grows large and eats coral. The small worms often find their way into the reef tank with live rock and, though they are really benign, aquarists often worry themselves sick over the sight of them because of the generic equation that bristleworm = bad. Unlike their larger cousins, these small worms eat detritus and uneaten food, and thus help to keep the spaces between gravel grains clear. They reproduce rapidly in gravel beds without any assistance from the aquarist. Their population explosion can appear unsightly to some aquarists, and it can be checked by including in the aquarium a pair of banded coral shrimp, Stenopus hispidus. Certain fish such as Pseudochromis springeri and P. aldahraensis, and some of the small wrasses will also eat these bristle worms and prevent the population from becoming too large. Commercially available worm traps may also be used to control the population (see Chapter 10).
Several other types of polychaete worms are introduced with live rock or with "live sand", if it is available. These multiply in the aquarium both sexually and asexually, and the result is a very live sand bed full of worms that actively feed on detritus and prevent the sand from becoming a dirt trap. Terebellid or "spaghetti worms" live in or beneath rocks, or in gravel-lined tubes they construct in the substrate. Their tentacles stretch several centimeters to over one metre in some varieties, such as A rnphitrite sp. Aquarists often believe the tentacles themselves are long thin worms. The tentacles "crawl" along the rocks and bottom, and trap particulate matter that passes down a thin groove running their length. Periodically the worm will defecate a large pile of detritus that it has collected and ingested. Similar to the terebellid worms are spionid worms. Like terebellids they live in rocks, beneath them, and in tubes in the sand, and they have long tentacles that collect particulate detritus. The distinguishing characteristic of spionids is that they have only two tentacles, whereas terebellids have many.
Sandy areas in coral lagoons, around seagrass beds, and intertidal mudflats often have another type of substrate dwelling worm that can be beneficial in large reef aquariums with a thick sand bottom. The "lugworm", Arenicola spp. makes what looks like a small volcano in the sand, with the occasional plume coming out the top and all. It lives deep in the sand, and has two "openings" to its burrow. The volcano mound opening is the side from which the worm defecates ingested sand, and the pile created rises like a
Serpent starfish are excellent scavengers. They feed on fish feces and uneaten food. J. Sprung.
cone with a hole in the center. Water normally enters through this hole, and the worm sends a current toward the exit of its burrow, causing the sand at the surface to cave in like a sinkhole. The sinking sand from the surface is rich in detritus, bacteria, and algae on which the worm feeds. WThen the worm defecates, the current is reversed. These worms literally turn the sand over.
Brittle starfish, a.k.a. "serpent stars" are also useful scavengers that eat feces or any missed food particles, and seek out and consume any organism that has died. Several should be included, especially in aquariums with gravel or coral fragments on the bottom. Serpent stars come in many colours and varieties. Having different types in the aquarium can be visually dramatic. When food is added, their writhing arms of many colours and patterns come out from the rocks. Some brittle stars remain beneath the rocks or gravel, where they continuously move the substrate in search of edible detritus; sand grains moving along their legs as if on a conveyer belt.
Tiny hermit crabs described in chapter 9 under the topic of herbivores, are good scavengers and very effective at preventing algae from coating sand or gravel.
Finally, the use of alternating currents, surge waves, or strong circulation will greatly assist the management of a thriving sand or gravel bed. The water circulation maintains the healthy population of microorganisms and invertebrates living there, wThile keeping the oxygen levels in the aquarium above saturation. We present here some decorating ideas for the creation of an aesthetically pleasing display.
Aquascaping plans, viewed from above a. A reef built in the center of a long rectangular aquarium affords viewing from at least three sides, the fourth side being obstructed by the overflow chamber, if present. Note direction of water flow creates circular motion and sweeps surface water over the overflow wall.
b. In this plan the reef is shaped in a spur-and-groove fashion, providing many surfaces for decoration. A corner overflow is installed with the water return directed to sweep surface water toward it. A powerhead (or two) controlled by automatic pulse timers sends surge-like water motion over the reef front.
c. This reef aquarium is poorly planned and aquascaped. The rocks are stacked like a wall against the back of the aquarium- easy to build but BORING! The water flow is directed away from the surface skimming overflow, resulting in accumulation of a surface slick at the opposite end.
d. This reef aquascape was planned to model on a small scale the shape of the whole reef. A wave bucket sends a surge of water over the reef. See the description of
Dr. Adey's system in chapter 5,
A reef aquarium aquascape similar to the plan in 7.1 b.
Notice the open construction ol the live rock structure. J. Sprung.
More Aquascaping plans, viewed from above a. This square aquarium has a reel structure built in the center. Two powerheads provide circular movement of water. The reef can be viewed from all four sides. An overflow could be installed in the center. We have left out the overflow to demonstrate the possibility of a reef aquarium without one. An internal protein skimmer could be used, and a level switch could be installed in the aquarium for top off of evaporated water.
b. This wide reef aquarium has the reef structure built along the sides with a coral bommie in the center. With this design the effect of a coral grotto is created.
Construction of a Pacific reef exhibit at the Waikiki Aquarium, Honolulu, Hawaii. Concrete cinder blocks were used beneath the live rock structure. The cinder blocks first had to be cured in freshwater with weak acid for several weeks to remove excess alkaline substances they initially leached into the water. Note use of plastic cable ties. B. Carlson.
The reef structure is complete, and some corals are added. B. Carlson.
After several months the exhibit is a growing, healthy slice of reef. B. Carlson.
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The word aquarium originates from the ancient Latin language, aqua meaning water and the suffix rium meaning place or building. Aquariums are beautiful and look good anywhere! Home aquariums are becoming more and more popular, it is a hobby that many people are flocking too and fish shops are on the rise. Fish are generally easy to keep although do they need quite a bit of attention. Puppies and kittens were the typical pet but now fish are becoming more and more frequent in house holds. In recent years fish shops have noticed a great increase in the rise of people wanting to purchase aquariums and fish, the boom has been great for local shops as the fish industry hasnt been such a great industry before now.