Deepwater Reef Aquarium

Setting up a deepwater reef aquarium.

During the last decade reef aquariums have become increasingly popular. These aquariums emphasize the culture of various invertebrates, such as stony and soft corals, anemones, photosynthetic clams (Tridacna spp.), mushroom anemones (Actinodiscus spp.) and various types of macroalgaes. Culture of these specimens demands water of very high quality, and, as a result, reef aquariums commonly utilize trickle filters and protein skimmers. Despite the challenge of maintaining such exceptional levels of water quality in this type of system, success rates are generally high. Indeed, few aquariums are as breathtakingly beautiful as a healthy, fully stocked reef aquarium.

Reef aquarists have reported great success in their aquariums with photosynthetic animals, but many of these hobbyists have failed with a number of the most beautiful species of saltwater invertebrates. Aquarists have almost given up on some of the very beautiful soft corals (Dendronephthya spp.), many unbelievably colorful sponges, the beautiful horn corals (also known as gorgonians) and the exquisite cup or sunflower corals (Tubastrea aurea). There is a very simple reason why these animals do not thrive in reef aquariums — they are all deepwater invertebrates.

Contrary to what some aquarium literature may lead you to believe, not all invertebrates are found within 10 feet of the water’s surface! Many invertebrates that we attempt to keep in reef aquariums normally live at depths of 50 to 90 feet (or on the shaded undersides of overhangs and caves). These animals quickly burn to death in aquariums lit by metal halide, actinic or other sources of bright light. The only way to keep these animals successfully is in a deepwater reef aquarium.

The immediately apparent advantage of a deepwater reef aquarium is that it requires very little light. In fact, this type of system needs only enough light to view the animals. For example, an aquarium that is 48 x 22 x 15 inches or about 75 gallons needs only 40 watts of fluorescent light. Not only does the need for reduced illumination cut down on your electric bill and eliminate the need for an expensive lighting system, it also reduces the amount of heat generated, which is crucial in a deepwater reef aquarium.

Although a deepwater reef aquarium requires less light than a photosynthetic reef aquarium, the need for efficient biological filtration is still necessary. A well-designed trickle filter can be used along with a protein skimmer, although only a protein skimmer need be used when there is a lot of live rock in the aquarium. Dissolved organic pollutants are just as much a problem in a deepwater reef aquarium as they are in any other densely stocked aquarium. Basic information about trickle filters, protein skimmers and ozone can be found in a number of books and on

Animals found in the deeper locations of a reef need to be maintained at temperatures slightly cooler than those residing nearer the surface. Ideal temperatures are in the range of 72 to 76 degrees Fahrenheit. Don’t expect to maintain a significant growth of algae in a deepwater reef aquarium — few algaes are found at these depths. To the contrary, algal growth on sponges, gorgonians and soft corals is one reason why these animals are difficult to maintain in photosynthetic reef aquariums. Microalgae growing on the surface of a sponge will eventually kill it. The sponge is unable to filter tiny food particles out of the water and it slowly starves to death. Gorgonians do not extend their polyps if they are covered with algae, and soft corals do not inflate to their majestic fullness if their spicules are choked with algal growth. The successful deepwater reef aquarium is an aquarium filled with live rock and colorful invertebrates, but no algae.

Although some of the animals that thrive in a deepwater reef aquarium are found at great depths, others live at relatively shallow depths but in locations that are shaded from light, such as caves and the undersides of overhangs. These areas have virtually the same environmental conditions as the deeper areas (i.e., low light, little marine algae growth and strong current).

Some aquarists may doubt it’s possible, but a deepwater reef aquarium can actually be more colorful than a photosynthetic reef aquarium. Most photosynthetic invertebrates are shades of green, brown, beige or white. Actinic lights artificially enhance the blues and greens, making the animals more colorful than they would be in nature. On the other hand, deepwater invertebrates are found in a wide variety of colors. Deepwater sponges can be blue, yellow or violet, while gorgonians are found in fluorescent hues of purple, green, red, orange and yellow. Few corals are as colorful as a colony of Tubastrea aurea, with its numerous orange polyps and yellow tentacles forming a vivid bouquet of color. This is a sight the photosynthetic reef aquarist with a brightly lit aquarium will never see.

When adding live rock to a deepwater reef aquarium, use the same amount that you would for a shallow water reef aquarium — 2 pounds of rock per gallon of water. This is, of course, a rough guide. You can have a successful reef aquarium by using more or less than this amount. Live rock is usually available in two grades, known as “base rock” and “decorative rock.” Base rock is usually for sale at half the price of decorative live rock. I recommend using approximately 75 percent base rock and 25 percent decorative rock. This allows a natural looking display at great savings. However, even base rock is not inexpensive.

At the time of this writing, live rock shipments from Florida have been suspended, and the price of live rock has increased accordingly. As you are reading this the supply of live rock may either be abundant or restricted. In the latter case, you may use many other substances for the base rock. Many types of calcerous rock are available at an equivalent or lower cost than base rock. Some of this rock is sold under the name “tuffa rock.” In the future, I think reef aquarists will be using this and other substances as a base for their reef aquariums, because it is less expensive and because of environmental concerns.

Several species of saltwater invertebrates thrive in a deepwater reef aquarium. We have already mentioned Tubastrea aurea. Other similar species are Tubastrea tenuilamellosa, Astrodies calycularis and Balanophyllia gemmifera. These are stony corals, and their corallites are colored a bright orange. They differ from most shallow water stony corals, which have whitish-colored corallites.

A corallite is the stony structure that supports and encloses the soft polyp. At night, when these corals extend their yellow polyps to feed, the corals resemble a bouquet of flowers. They are some of the easiest corals to maintain as long as you do not attempt to keep them in a brightly lit aquarium.

Stony corals should be fed two to three times weekly after they have fully extended their tentacles. Often, you can stimulate these corals to open by first feeding other invertebrates or fish in the aquarium. The coral will sense food in the aquarium and prepare to feed. You can feed these corals with live brine shrimp, thawed frozen brine shrimp or plankton, and small pieces of shrimp, clam or squid.

The easiest way to feed them is to purchase a squeeze-bulb baster from the housewares section of a grocery store. Thaw the food in a plastic cup and draw it into the baster. Place the baster in the aquarium and direct a small puff of food at the coral. It is important to gently puff the food at the coral — if you squirt food at the coral too quickly, you will startle the animal and it will withdraw its tentacles. These corals, as is true with most corals, should be exposed to a strong current of water. The current brings food to the coral, washes away metabolic waste and keeps the animal clean.

Sponges are a large group of invertebrates that thrive in a deepwater reef aquarium. A few examples are the blue crust sponge (Haliclona permollis), the yellow cup sponge (Verongula spp.), the violet barrel sponge (Siphonochalina spp.), the yellow tree sponge (Raspailia hispida), the yellow ball or moon sponge (Cliona spp.), the cork sponges of the genera Tethya, Suberites and Pseudsuberites, the bath sponges (Euspongia officinalis) and the horse sponge (Hippospongia communis). The purple sponge (Lotrochata purpurea) is one of the loveliest examples.

Sponges are filter feeders that feed on the tiniest particles of foods. The animal will die if it becomes coated or clogged with particles. Therefore, you should not attempt to feed sponges directly. Instead, rely on residual amounts of food left over from feeding other animals to supply the needs of the sponges.

If handled properly, sponges will grow and multiply throughout your aquarium. Sponges, however, are very sensitive to exposure to air — never hold one out of the water for more than a few seconds. When you buy a sponge from a dealer, make sure it is bagged while completely submerged in water.

Some of the most lovely invertebrates for the deepwater reef aquarium are the soft corals. Some good candidates include the yellow Dendronephthya aurea, the red and white Dendronephthya divaricata, the orange-red Carotaleyon sagamianum, the red-white Dendronephthya klunzingeri and the pink-white Scleronephthya spp.

Some soft corals are fully expanded during the day, whereas others are nocturnal. Soft corals are very fragile, and it is difficult to place them in the aquarium without damaging them. It is therefore recommended that you purchase only specimens that are still attached to their rock base. The animal may live if it has obviously been detached from its rock, but the odds are against it.

Gorgonians are some of the most common corals on the reef, particularly in the Caribbean. They are lovely, colorful filter feeders that depend on strong currents to bring them food and to keep them free of debris. Few invertebrates are as fascinating to me as a red finger gorgonian (Corallium rubrum) with its lacy white polyps waving in the currents of an aquarium. You can watch a single polyp catch a food particle, close up on it and reopen a few minutes later for more food.

Gorgonians require optimal water quality and are the earliest indicators of trouble in your aquarium. I can determine the water quality in my aquarium simply by glancing at the gorgonians. Their polyps won’t be fully extended if there is a slight trace of ammonia in the water, the pH has dropped slightly or the protein skimmer needs cleaning. Think of the money you will save in test reagents!

Several species of gorgonians are commonly available in the hobby. These include the red finger gorgonian (Corallium rubrum), the orange finger gorgonian, the purple frilly gorgonian (Pseudopterogorgia spp.), the purple whip gorgonian, the purple sea fan (Gorgonia flabellum), the green whip gorgonian (Ptergorgia citrina), a lovely shallow water white gorgonian (Eunicia spp.) and a purple tree gorgonian that sometimes goes under the name “anemone tree.”

A fascinating animal that has been very difficult to maintain in captivity is the feather starfish, or crinoid. The basket starfish has also been almost impossible to maintain in conventional aquariums. Although I have not attempted to do so, it seems to me that if these animals will ever be maintained in aquariums, the deepwater reef aquarium is the place to try. It would certainly be a challenge to maintain these animals in captivity.

Tube anemones (Cerianthus spp.), which should not be kept in shallow water reef aquariums, will thrive in a deepwater reef aquarium. These animals are really not anemones but rather strongly stinging animals that will kill other anemones, stony corals and soft corals. They burn quickly under the intense light of a shallow water reef aquarium, but do well in dimmer light. These animals are available in white, orange and purple. As long as their tentacles cannot reach other animals, they are ideal residents for a deepwater reef aquarium. You should be aware, however, that they are particularly adept at catching and eating small fish in an aquarium. Don’t keep tube anemones if you also plan to keep expensive saltwater fish, such as resplendent angels or Red Sea basslets!

Bubble corals (Plerogyra sinuosa) also do well in the deepwater reef aquarium, although they should be placed in a position where they receive some light — they do not require total shade. Bubble corals do well in both deepwater and shallow water reef aquariums.

Other miscellaneous invertebrates that do well in deepwater reef aquariums are starfish, featherdusters, Christmas tree worm colonies, flame scallops, thorny oysters, jewel box clams, the cock’s comb oyster (Lopha cristagalli), sea pens (Pennatula spp.), most shrimps, crabs and lobsters (although crabs and lobsters should be omitted from aquariums containing soft corals), sea cucumbers, sea squirts (tunicates), bryozoans and some other zooantharians that are not dependent upon sunlight. Incidently, beware of the chocolate chip starfish! It is a very carnivorous species and has been known to eat leather corals, soft corals, mushroom anemones and other starfish!

I hope some of you will be inspired to try a deepwater reef aquarium. In my opinion, it is the most colorful, interesting and fascinating type of reef aquarium.

Of course, because we often want to try to do everything in one aquarium, it is certainly possible to design an aquarium with shaded areas for deepwater invertebrates and brightly lit areas for the photosynthetic animals. In this type of setup, however, the microalgae that grow in the brightly lit portion tend to float around and foul the deepwater invertebrates. The purist will want to set up a separate aquarium for the deepwater specimens. 

Deepwater Fish
There is certainly a place for saltwater fish in the deepwater reef aquarium. The fish listed here are actually suitable for either shallow water or deepwater reef aquariums.

Basslets (Gramma spp., Pseudochromis spp.)
Combtooth blennies (Escenius spp.)
Eyelash blennies (Cirripectes spp.)
Lyretail blennies (Meiacanthus spp.)
Firefish (Nemateleotris spp.)
Torpedo gobies (Ptereleotris spp.)
Partner gobies (Amblyeleotris spp.)
Sleeper gobies (Valenciennea spp.)
Coral gobies (Gobiodon spp.)
Neon gobies (Gobiosoma oceanops)
Watchman gobies (Cryptocentrus spp.)
Mandarin dragonets (Synchiropus spp.)
Small sailfin gobies (Emblemaria  hypacanthus)
Jawfish (Opistognathus spp.)
Damsels (relatively peaceful species: Parma  spp., Chromis spp. and Chrysiptera spp.)
Pygmy angels (Centropyge spp.)
Anthias (Anthias spp.)
Seahorses (Hippocampus spp.)
Pipefish (Doryrhamphus spp.)
Wrasses (gentler species):
Velvet wrasses (Cirrhilabrus spp.)
Neon wrasses (Halichoeres spp.)
Leopard wrasses (Macropharyngodon spp.)
Lined wrasses (Pseudocheilinus spp.)
Parrot wrasses (Paracheilinus spp.)

Article Categories:
Fish · Saltwater Fish