My First Reef Aquarium

by Andrew Blumhagen

What do you think of when you imagine a captive coral reef? Certainly the beautiful colors, variety of shapes and alien textures of living corals come to mind, as do flashes of the gaudy hues of small fish darting in and out of their hiding places. A closer look might reveal comical hermit crabs picking tiny delicacies from the rock and snails grazing on an invisible layer of algae. Perhaps a feather duster worm suddenly retracts its delicate tentacles as it senses your shadow, or a shrimp dances in the current as its antennae sweep the environs looking for its next meal. But as soon as you are entrenched in this underwater reverie, you realize that the equipment alone for this wonderful creation costs more than half a year’s rent and that the invertebrates are more sensitive than wild-caught discus - ready to crash spectacularly the moment your visiting mother-in-law sneezes in the wrong direction. The plumbing looks like the inner workings of a steam engine, the fish never seem to last for more than two weeks and the water chemistry would baffle a Nobel laureate. Who needs the trouble when you can go to a public aquarium and see the same magic without the hassle? Heck, even a SCUBA tour of the Solomon Islands would be cheaper! Well, believe it or not, you’re now going to learn how to re-create this delicate but beautiful environment for about two hundred dollars and one hour of maintenance each month.


The micro-reef aquarium described here is centered around the Eclipse System Six. The Eclipse incorporates the tank, hood, filter and light into a compact unit that sits on any flat surface capable of supporting 75 pounds. It measures 16" long by 8" deep by 14.5" tall and holds (you guessed it!) six gallons of water. The front curves outward to create a magnifying effect and the sides taper slightly towards the rear. The tank’s construction of high-quality acrylic also enhances the appearance of the system. The hood contains an 8-watt fluorescent light completely covered by a plastic shield, a small pump that feeds the filter, a floss and carbon cartridge, and a Biowheel. The hood is completely sealed so that the reef critters stay in the tank and everything else stays out. The Eclipse System Six retails for approximately $60.

As small and simple as the Eclipse System Six is, it performs all of the functions necessary to sustain a simple coral reef aquarium. The fluorescent bulb is bright enough for hardy corals and other sessile invertebrates that will be described later. The bulb included with the Eclipse is a broad-spectrum daylight bulb that is perfect for the reef, however a bulb with a stronger blue spectrum, such as a Power-Glo bulb, which will set off the inflorescence of certain corals may be substituted. The purpose of the floss and carbon cartridge is fairly obvious, though it’s important to maintain fresh carbon in a small system such as this to absorb accumulations of dissolved organic material. The Biowheel provides efficient wet/dry filtration for the system and keeps the water well aerated. Due to the inherently high amounts of dissolved solids in saltwater, it holds much less dissolved oxygen than freshwater does, therefore the Biowheel becomes an essential component of the system.

If the system is placed in a room where the ambient temperature drops below 70°, a small, submersible heater will be needed. A 25 watt VisiTherm heater, which retails for about $15, is ideal. The optimum temperature is 75°, but keep in mind that the light and pump will add about four degrees to the system. A timer for the light is essential, as a consistent photo period of 11 to 12 hours per day is necessary to maintain healthy corals. The timer can be purchased at any hardware stores for about $5. This is all the equipment required for the reef aquarium, except for certain maintenance items that will be discussed later. So far, we’ve only spent $80.


What makes a reef tank a reef tank? Primarily, it’s the presence of live rock. Live rock, as its name implies, is coral skeletons that have become inhabited by bacteria, micro and macroalgae, worms, sessile invertebrates, like corals, anemones, sponges, crustaceans and other marine organisms. It serves as the building blocks for your reef, as well as fulfilling a number of other important functions. Most important is the biological function it performs. Live rock actually reduces organic wastes from the fish and other animals living in the aquarium. The coralline algae (pink, purple or red microalgae with calcareous or calcium-containing cell walls) absorb nitrogen and phosphorous just as live plants do in a freshwater aquarium. In addition, live rock is full of holes, tunnels and crevices. These provide perfect habitats for denitrifying bacteria. In the outside of the hole, aerobic bacteria perform the familiar nitrification process (which is the same in saltwater as it is in fresh, though with different bacteria species) of converting ammonia into nitrites, then nitrites into nitrates. Toward the back of the hole where oxygen has become scarce, denitrifying anaerobic bacteria complete the cycle, converting nitrates into nitrogen gas. In addition to providing habitats for your animals, plants and bacteria, live rock also introduces a wide variety of organisms into your tank. These provide a diversity of organisms that can serve as food to other reef inhabitants but mostly delight the aquarist as they are observed popping out of nowhere and growing into recognizable forms.

In this system, six to eight pounds of live rock will be needed. It’s important to remember that the corals to be added to the system will come attached to live rock as well. Four or five pounds of live rock is a good starting point. To select live rock, use your eyes and your nose. Look first for rock encrusted with coralline alga. Coralline alga is an extremely important component of the reef system. It is distinctively pink, red or purple and feels like wet chalk. In addition to removing organic wastes, it prevents unwanted algae from taking charge of the tank as other algae are not able to grow on top of it. Next look for other organisms attached to the rock. Macroalgae (seaweed) is good for the tank and aesthetically pleasing. Live corals, sponges, tubeworms, snails and other animals are generally desirable as well. Basically, the best live rock is the live rock with as much "stuff" growing on it as possible. Look also for interesting shapes that will be used to construct the reef. After looking at the live rock, give it a good sniff. If it smells foul, don’t buy it. It should smell like a clear ocean breeze, not a rotting pile of seaweed or a bait bucket that’s been left in the sun. Premium live rock tends to cost between $5 and $7 per pound.

No furnishings other than live rock are needed for the system, however it may be more aesthetically pleasing to cover the bottom of the aquarium with gravel instead of keeping a bare tank floor. Use a small amount of crushed coral or aragonite gravel, at most 1/2" thick, preferably 1/4" or less. The size of the gravel does not particularly matter for the thin layer that will be used here. So far the total cost of the system is about $130.

Setting Up:

The obvious first step is to select a location for your micro-reef. It should be placed where it is easily viewed and readily accessible for feeding and maintenance. Direct sunlight should be avoided; it may cause undesirable algae growth on the acrylic and sudden spikes in water temperature. As mentioned above, any flat, sturdy surface that will support 75 pounds is perfect. This can be a dresser in the bedroom, a desk at work, the kitchen counter, or the top of a toilet tank. The easiest way to test whether the surface will hold the aquarium is to sit on it first. If it breaks, find another surface. If it doesn’t, it’s plenty strong.

The quality of the water used in the micro-reef is extremely important. The presence of organic chemicals, pesticides, chlorine, and fertilizers will assuredly ruin your hopes for a healthy reef in spectacular fashion. Similarly, traces of metals in the water like copper, iron, lead or mercury will destroy your invertebrates and likely your fish as well. While it might be assumed that the water is safe simply because it comes from the tap, a review of a printout from the local water company will probably be enough to warrant another source of water. It is probably wisest to use a de-ionization or reverse osmosis filter on the water to be used in the reef. If these are not available, distilled water can be purchased at the drug or grocery store. It’s only a six- gallon tank, after all.

The salt mix must also be of the highest quality. Tropic Marin and Reef Crystals are premium salt mixes which contain all of the necessary trace elements and buffers for a healthy micro-reef. A bag of premium salt mix that makes fifty gallons of saltwater costs less than $20. A hydrometer will be needed for mixing the salt with the water to the appropriate salinity. This is a device that measures the specific gravity (spg) of the water, thereby indicating how much salt is dissolved in the water. A SeaTest hydrometer made by Aquarium Systems is sufficient for our purposes and costs about $12. It must be mentioned that specific gravity and salinity are two completely different attributes of water. Salinity is the measurement of dissolved ions in the water. Specific gravity is the density of the water (weight/volume). For the purposes of keeping a relatively simple microreef the distinction is not particularly important.

Now, we’re ready to fill the Eclipse. Start by mixing five gallons of saltwater in a five-gallon bucket. This may not be quite as easy as it seems. The first time you mix saltwater, use a set of measuring cups. For five gallons of water at least a cup of salt mix will be needed. Mix the salt into the water — with clean hands (free of soap, hair products, nicotine, grease or anything else). A long-handled spoon or other mixing device could theoretically be used but it’s not likely that the hands will stay dry anyway during setup or regular maintenance. The water will initially be white and cloudy. Let it sit until it clears, then measure the specific gravity with the hydrometer. The target spg will be 1.022 to 1.023. This is slightly higher than might be used in a fish-only aquarium but slightly lower than the average spg of the tropical oceans. If needed, add additional salt mix in small increments, each time allowing the salt to completely dissolve before measuring. Keep track of how much salt is put in each increment and when the target is reached, add up the increments so that the amount of salt mix needed for five gallons of water can be recorded or memorized.

Pour about half the water into the Eclipse and set aside the rest for the moment. If any gravel is to be used it should be added at this point. Make sure it is very well rinsed or it will cloud the water and leave nasty-looking deposits on the inside of the acrylic. Now the tank is ready for live rock. Remove any wrapping that the live rock may have come with and simply place it in the tank. The live rock should be stacked to about two thirds the height of the aquarium. Be creative in this process; all too often reef tanks look like they were assembled like brick walls, unnatural and regular like they were, well, man-made. Use a good amount of time turning the rocks all different directions, making caves, coves, spires, shelves and other features that the inhabitants will eventually weave in and out of, or perhaps claim as their exclusive territory. Pieces of live rock often have a "good side" with noticeably more organisms growing on it. Put that side facing out and up so that the organisms can be viewed, and will receive the light that feeds them. The reef should not actually touch any of the walls of the tank as this will likely create dead spots devoid of essential water circulation. Take care that the rocks are stable since a freak landslide may kill prized corals or shrimp. To check, give the stack a gentle push from several different directions to make sure they’re securely in place. It will be very difficult to rearrange the rocks once the reef is established, so make sure that reef the looks good, even without animals. Once the reef is built, add the remainder of the water and place the hood on the tank. Turn on the filter and let it run for a few days before turning on the light.

Now comes the hard part, the waiting game. Live rock often needs a good amount of time to "cure" once it’s in the aquarium. Some of the organisms on the rock die from the stress of transportation and changes in water. The rotting corpses cause nutrient spikes, creating an environment that will not support any of the animals that the reef will eventually maintain. One of the best ways to measure the curing process is by watching alga growth on the tank walls and on the rocks. Initially, algae will grow very quickly. As the live rock cures, it will slow down to a manageable level with regular maintenance. While the live rock is curing, water changes of about two gallons every week may be needed to reduce nutrient levels in the tank. Once alga growth slows down, it’s time to start adding animals to the tank.

There are two problem algae to watch out for during this period and during regular maintenance. Cyanobacteria is readily recognizable. It coats the substrate and furnishings in an ugly layer in a variety of colors from blue-green to red to black, hence its more common name, slime algae. Fortunately it is easily removed. Simply start a siphon with a narrow, flexible tube and suck it right off the substrate. Replace the waste water with newly mixed saltwater. Slime algae are not only ugly, but they can smother other beneficial organisms blocking light and nutrients. The other problem algae are filamentous or hair algae. This looks like green fuzz growing on the rocks and is very difficult to remove once it has a foothold. At the first sign, initiate weekly water changes of two gallons. Start adding algavores (see livestock selection below) to attack the hair algae already in place. In the worst-case scenario, the rocks may have to be removed and scrubbed with a stiff-bristle brush dedicated to this purpose. Hair algae are not particularly dangerous to the reef organisms but it looks bad and prevents other beneficial organisms like coralline algae from growing.


This is the fun part. Finally, the animals that inspired this project in the first place can be added. Don’t get too carried away, though… the first rule of successfully starting a micro reef is to go slowly. There is a natural progression in which the animals should be added to the tank. First start with algavores. These serve an important purpose in the reef, but don’t need to be boring or unnoticed. There are essentially three choices for the cleanup crew: hermit crabs, snails, and algavorous fish. Most fish, like tangs and lawnmower blennies, grow too large and are too aggressive for the six-gallon Eclipse, so they can be ruled out entirely. Once the problem algae are under control and the live rock appears to be growing coralline algae and other "good" organisms like feather-duster worms, sessile (non-moving, like corals) invertebrates may be added. If all goes well, a fish or decorative shrimp may be added to complete the system. Of course, it’s not necessary or even advisable to keep all of the various decorative organisms discussed here. Space and nutrient management are the key to a successful micro-reef aquarium.

Two species of hermit crabs are appropriate for this system, Blue-Legged (Clibanarius tricolor) and Scarlet-Legged (C. digueti, also known as Red-Legged or Mexican Red-Legged) Hermit Crabs. Blue-Legged Hermits are easily identified by (no surprise here!) their blue legs with white and red bands at the joints. They are also somewhat smaller than their red cousins. Scarlet-Legged Hermits are easily identified by their astonishingly bright red legs. Their bodies are a pale orange or pink color. Hermit crabs are ubiquitous to all reef aquariums, barring only those that contain predators. A few moments watching them reveals why. Hermits are sufficiently entertaining to merit their own tank and look especially good featured in a small system. They scramble over the reef, daintily picking morsels from the rock while dragging their disproportionately large homes on their backs. You may periodically find "corpses". Before you despair an untimely death in the tank, realize that these are probably molts left behind by the growing Hermits. The addition of a few snail shells (usually available from the retailer that sold you the Hermits) may be a good idea to keep the little clowns from trying to evict a compatriot from its own shell as they grow out of their old ones. Hermits are excellent algavores and will also consume any uneaten food in the aquarium. In a six-gallon reef, as many as a dozen Hermits may be maintained, perhaps more, and the two species may be combined. Start by adding six or eight total. If a hair alga problem is evident, add more. Hermits usually cost two or three dollars each.

Another useful and popular algavore for the microreef aquarium is the Astraea (Lithopoma tectum) snail. These small snails, which look like rounded, spiral turbans with small lines of knobs following the spiral, readily eat diatoms (brown algae) and filamentous algae. I recently added five of these snails to a 45- gallon marine aquarium and they ate a substantial layer of algae on the front glass in less than a week. Astraea snails should not be confused with their larger cousins, Turbo sp. snails. Turbo snails, while also excellent algavores, grow too large for a small system. Check with your retailer to make sure you buy the right species. Astraea snails eat substantially more than hermit crabs, so fewer are needed. Start with two or three, but only if there is a discernible layer of algae for them to eat. They may starve otherwise. If these are not controlling alga growth after a couple of weeks, add one or two more. Five or six Astraea snails are probably the limit for this reef system. They should cost about the same as hermit crabs.

Now that the live rock has cured and problem algae are under control, the system is ready for corals and their close relatives. There are thousands of species of corals in the world’s oceans and probably hundreds available in the aquarium trade. A few of the easiest to keep will be discussed here. First, however, there are a few important general concepts to understand about corals and other cnidarians. Cnidarians (formerly Coelenterates, for those folks that may have taken high school biology before the reclassification) are animals, even though they may look quite vegetative or even alien. The phylum Cnidaria encompasses corals, anemones, jellyfish and hydras. The distinguishing feature of a cnidarian is its stinging cells. The cells contain a small harpoon, which is triggered by physical, electromagnetic or chemical stimuli. These harpoons come in many shapes, and may contain varying levels of toxins which may be injected into a predator, intruder, or ill-placed neighbor. Practically, this means that any cnidarian must not touch any other animal in the aquarium. Damage or death to one or both of the animals in question will certainly ensue. Most cnidarians kept in aquaria are structured as polyps. Large, single specimens, like anemones, can be up to three feet across. Others, like small polyp stony corals, are large colonies of tiny polyps attached to each other’s tissue. A polyp has a foot at the bottom, a mouth at the top and a column in between. There may be tentacles around the mouth that can grab food and stuff it into the mouth. Rudimentary digestive organs, called mesenteries, are found inside the body column. Polyps usually only have one or two layers of cells and so are very delicate. The bulk of the polyp’s mass is actually seawater; polyps can control the amount of water between cell layers and thus extend or contract depending on the situation. Many marine cnidarians have a symbiotic relationship with zooxanthellae, which are photosynthetic algae that live inside the cnidarian’s cells. Zooxanthellae feed on the waste chemicals that are produced by the cnidarian and in turn produce sugars and other compounds, which the cnidarian uses as an energy source. These photosynthetic algae are the reason that a powerful light source of the appropriate spectrum and photoperiod is so important to the success of many corals and their relatives in captivity. Cnidarians are also able to absorb minerals and organic compounds directly from the ambient water. Ammonia, in small amounts, is actually an important nutrient for many cnidarians; calcium, magnesium, carbon and other minerals are also important. Only healthy cnidarian specimens should be purchased from a retailer. They should be well extended with uniform colors and without rips in the tissue. Bleached or patchy specimens are unhealthy and should not be purchased. Damaged specimens will not recover. Generally speaking, if the specimen looks good, it is probably healthy.

Corallimorpharians, commonly known as mushroom anemones or mushroom corals, are one of the most popular cnidarians found in aquaria. These are individual polyps that look like disks with a small mouth in the center. They attach themselves to a hard substrate by a foot on their undersides. Mushrooms come in an astonishing variety of colors from red to blue to green to many shades of brown. They can have stripes, spots, rough textures or smooth. They come from pristine reef waters and muddy harbors. There is truly a mushroom for everyone. Mushrooms utilize photosynthetic zooxanthellae but don’t necessarily need as much light as their stony cousins. Fortunately, they let you know what they think of their habitat. If they are getting too much light, they will not fully extend or will shrivel before the light goes out. You can solve this by placing the mushrooms farther down in the tank or in the shade, or by tilting the rock so that the light does not hit the them directly. If they are not getting enough light they will extend themselves upward toward the light in a trumpet shape. This is also easily solved by moving the mushrooms up in the aquarium or by tilting them so that they can absorb more direct light. Over time, mushrooms will adjust the amount of zooxanthellae in their tissues to the level best suited to their environment and individual needs. They may also need a little help from the aquarist to adjust. If new mushrooms are not faring well, the photoperiod can be reduced to eight or nine hours per day, then gradually increased. Too much light can be a problem as mushrooms will actually "overeat" leading to high levels of dangerous hydrogen peroxide in their tissue. Iodine supplements can ease this problem (see the "Maintenance" section below). Healthy mushrooms are likely to reproduce in the aquarium. Frankly, this is a rather odd process. A glob of slimy-looking tissue is extended from the parent mushroom. A mouth will appear on the glob and the mushroom will start to take shape. Once the clone can support itself, the connection to the parent will be severed. Mushrooms have a couple other "behavioral" idiosyncrasies. Some species actually feed by catching prey or debris on their discs. Once dinner is secured, the mushroom will turn itself inside out to consume it. In this state they look like rotting figs. When mushrooms are disturbed they may expel their mesenteries (digestive organs). These twisted, white strings will be reclaimed in a few hours.

Another hardy choice of cnidarians for the micro reef is zoanthids, or zoanthid polyps. These are small, individual polyps that live in dense colonies but, with a few exceptions, are not actually attached to one another at the base of each polyp. Zoanthids also utilize zooxanthellae and should be placed where they will receive maximum light levels. They are particularly vulnerable to the stinging cells of other cnidarians so particular care is needed in placing them with a buffer zone between them and their neighbors. Healthy zoathnids will also reproduce in this system. A bud will appear at the foot of the parent polyp and will grow into a full-sized clone. As with corallimorpharians, the clone will separate from the parent once it is self-sufficient. Zoanthids can reproduce rapidly in and may cover large areas of live rock in the tank. If your colony is "too" successful, it may be necessary to remove covered live rock and return them to the dealer or trade them with a friend. Perhaps the most popular zoanthids are Yellow Polyps (Parazoanthus sp.). As their name suggests, they are yellow in color, ranging from dark mustard to bright sunshine shades. They look essentially like hydras with tall columns and long tentacles extending from the crown. Their mouth is a bright yellow knob in the center of the tentacles. Most other zoanthid varieties have a wide disk on top of a stalk, with a ring of tentacles around the rim of the disk. They are usually brown and may have green iridescence and/or a brightly-colored center and mouth. Identification of these species is tricky but care for all of them is the same. In fact, many zoanthid colonies for sale actually contain more than one species. Common varieties are sold as Button Polyps, Sand Polyps, Colony Polyps, Sea Mats (these are the polyps that attach to one another at the base) or simply Zoanthid Polyps. Take note that not every cnidarian sold as a "Polyp" is a zoanthid. Certain true corals, like Clove Polyps and Star Polyps, may have different requirements and should not be confused with zoanthids.

Corallimorpharians and zoanthids are not true corals. There are subtle morphological differences that distinguish them from corals, like the number of tentacles and the size and shape of the mesenteries relative to the polyp size. Few true corals that are appropriate for this system. A few that are often mistaken for zoanthids are exceptions: Green Star Polyps and Brown Star Polyps (Briareum spp.) could make a nice addition to this system. These look like zoanthids except that they form an encrusting brown or reddish mat from which the polyps grow. In a healthy colony, the mat will spread over the live rock and new polyps will pop up from the growth. Star Polyps may coat the inside wall of an aquarium, creating a very attractive backdrop. Care of Star Polyps is similar to that of zoanthid polyps except that they don’t need quite as much light. Pulsing or Pumping Xenia (Xenia spp.) is another popular soft coral but is more demanding than zoanthids or corallimorpharians. It has stalks from which branches of polyps extend. When healthy, the feathery tentacles make a grabbing motion, opening and closing while swaying in the current, but Xenia’s movement can pose a risk to other organisms in the tank. Make sure that branches do not touch other cnidarians as they sway in the current. Xenia is an active coral that provides fascinating movement in the tank. Xenia needs a lot of light, so it should be placed directly in the middle and top of the aquarium where the light is brightest. Varieties that are darker in color will be more successful as they have greater concentrations of zooxanthellae.

So what’s a fish tank without any fish? In this system, it’s perfectly reasonable to decide against keeping any fish. Most fish offered for sale in the trade will simply grow too big. If you decide to keep a fish, it should be added only after the population of cnidarians has been established for a few weeks. In my micro reef, I kept a single Pacific Yellowtail Blue Damselfish (Chrysiptera parasema, not to be confused with the Atlantic Yellowtail a/k/a Jewel Damselfish) very successfully. Yellowtail Damsels are striking royal blue with (no surprise here) a sunshine-yellow tail. They are playful and will spend much of their time in view. Their close relatives, Blue Devils, (Chrysiptera cyanea) also will not outgrow a six-gallon aquarium. Of course, the most popular family of marine fish for aquaria is the clownfish. The most popular species of the family, the Percula Clownfish (Amphiprion percula) will stay small enough to keep in the system. Perculas are bright orange with three white bars and varying degrees of black around the bars and fin margins. Their comical swimming motion and bright color makes them extremely endearing. A Percula should be kept as a single specimen to avoid overloading the tank with nutrients. Neon Gobies (Gobiosoma oceanops and G. evelynae) are another possible choice and are perhaps the only fish that could be kept in a small group of two or three. They are black with a neon blue or gold stripe from nose to tail. They are long and narrow and typically only grow to two inches long. Unfortunately, their natural life span is only about one year, so they would have to be replaced periodically. Another goby commonly offered in the trade, the Citron Goby (Gobiodon citrinus), might also be considered but only as a single specimen. Finally, several members of the Genus Pseudochromis, commonly called Dottybacks or Basslets, may be considered. The Orchid Dottyback (Pseudochromis fridmani), Strawberry or Magenta Dottyback (P. pophyreus) and Fairy Basslet or Bicolor Pseudochromis (P. paccagnellae) each stay small enough to live comfortably in this system. While selecting a fish at a dealer, make sure that there are no obvious problems such as torn fins or external parasites or infection. Ask the dealer to feed the fish before you purchase it to ensure that it has adapted to life in an aquarium. Feeding fish and the other reef denizens will be discussed in the "Maintenance" section below.

Besides fish and cnidarians, there are a few other decorative animals that fare well in a micro reef. Common Cleaner shrimp (Lysmata amboinensis) are beautiful crustaceans that add quite a bit of character to the tank. They are golden-yellow with a narrow white stripe down their back and a wider red stripe on either side of the white stripe. They have long white antennae that sweep around looking for food and potential predators. The Cleaner shrimp’s close relative, the Fire shrimp (Lysmata debenius), is another good choice. They also have long white antennae, but are colored deep scarlet with a few small white spots. Both species are cleaners in the wild, where they climb fearlessly onto large fish to pick parasites and bits of dead skin. They’ll even venture inside the mouth of ferocious predators, such as groupers. In captivity, they may learn to hop onto their aquarist’s hand to perform the same service. This is a trick that should be reserved for regular maintenance, when the water level in the tank is lowered and the aquarist’s hands are free of any contaminants. Either shrimp can be kept as single specimen unless there are no fish in the system, in which case two or three may be kept and the species may be mixed. Two species of commonly available crabs make good reef residents as well. Emerald crabs (Mithrax sculptus) are uniformly gray-green in color and make excellent algae grazers as well as adding interest to the micro reef. Sally Lightfoot crabs (Percnon gibbesi), which have narrow purple, orange, brown and yellow stripes, are also good algae grazers and move around quite a bit more than the Emerald crabs. Both of these are also best kept as single specimens in a micro reef. Finally, there is a family of segmented worms that make beautiful additions to reef aquaria. Feather Duster worms construct a tube or burrow to protect their body. They then stick a plume of tentacles out of the tube to trap plankton and floating debris. Small Feather Dusters are likely to appear in healthy live rock, but larger specimens are sold individually. They come in a wide variety of colors. Most of them have brown, gold and/or black striped tentacles, while others have pink and white stripes. When Feather Dusters sense movement, either by vibrations in the water or by sudden changes in light patterns, they rapidly suck themselves back into their protective tubes. After a few moments, they cautiously extend their tentacles again.

This list of animals should give a nearly limitless number of livestock combinations for a micro reef. The animals highlighted here are by no means the only ones appropriate, but are some of the most common and popular selections. There are many, many animals that are certainly not appropriate for this system. Anemones, Giant Clams (Tridacna spp.), and stony corals (with a few possible exceptions) will almost certainly not survive in this system. Any fish or crustacean that grows to more than two or three inches is not appropriate and many others may damage other animals in the aquarium. Additional research is a good idea; a few resources are listed below. Most importantly, never purchase an animal without knowing what its needs and behavioral traits are.


Maintenance of a micro reef should not be onerous and will become easy once a regular routine is established. Examine the aquarium’s inhabitants on a daily basis. Note any differences in behavior, appearance and health of the animals. If an animal dies, whether mobile or sessile (non-moving), remove it immediately. Otherwise, the byproducts of decay will completely disrupt the balance in the reef and cause harm to the other animals. Take note of extraordinary algae growth and take appropriate measures (described below) if it continues unabated. Water loss from evaporation should be replenished periodically with fresh water (evaporation removes only water, not salt!). The water level should not be allowed to drop more than a half inch below the top frame of the aquarium. Otherwise, the salt level will rise and the splashing will leave salt deposits on the insides of the tank and hood. If there are fish, shrimp, crabs and other larger decorative animals in the aquarium, they will need to be fed. Feed a small pinch of general marine flake food three or four times a week. If there are Feather Duster worms in the tank, crush a flake or two into fine powder and add it to the reef. There should not be any noticeable amount of uneaten food about one half hour after feeding. Hermit crabs and shrimp will clean up most leftovers. Most reef inhabitants will appreciate periodic feedings of live or frozen brine shrimp, brine shrimp nauplii and Daphnia, if available. Daphnia and newly hatched brine shrimp are particularly good for cnidarians and Feather Duster Worms.

Perform a one-gallon water change every two weeks. Make sure that your hands are clean before starting maintenance. It may be wise to rinse them very well in warm water to ensure that no soap, shampoo, grease or anything else is left on them. DO NOT wash your hands in soap just before maintenance. The traces left on your hands will be enough to kill many organisms in the tank. Before removing the hood to change water, remove any salt deposits (salt creep) that may have formed from splashing water around the filter. Remove the hood very slowly so that salt creep does not accidentally fall into the tank. Cnidarians can be burned by small pieces of salt that land on their tissue. If there’s a gravel substrate, a small vacuum and siphon should be used to remove detritus from the gravel. If there is no gravel, a siphon tube should be directed under and between rocks where detritus buildups are noticeable. Certain kinds of algae, such as cyanobacteria (slime algae) and filamentous algae, can and should be removed by siphon. Once a gallon of water or so is removed, wipe the inside of the aquarium even if there is little or no noticeable algae. Use an acrylic-safe sponge or pad, which is dedicated only to this reef system, to clean algae. It’s probably a good idea to mix saltwater 24 hours before adding it to the tank to ensure that it is completely dissolved and stable. As mentioned in part one, high quality salt mixes contain all trace minerals necessary to maintain healthy animals in the reef. Iodine is a possible exception. Iodine can reduce stress in corallimorpharians and encourage rapid growth of coralline algae. If your mushrooms and coralline algae are healthy, don’t bother with it. Iodine is quite toxic so great care must be exercised with it. Iodine reef supplements are available in liquid and powder form. Use half the suggested dosage for five gallons of water once a month. Liquid drops may be put into a small container of water and divided if needs be (it’s hard to measure half a drop!), then added to the mixed saltwater. Add the new water very carefully with the stream of water directed away from any cnidarians. Once the aquarium is refilled, replace the top and wipe the outside with a clean, dry, soft cloth. Acrylic can scratch! Test the cloth to be used on your cheek or inner arms to see whether there are any sharp particles or rough spots on the cloth that might scratch the tank. Every month the carbon and floss cartridge should be replaced. The light bulb should be replaced every nine to twelve months.

Trouble Shooting:

The biggest challenge in keeping a micro reef is controlling algae. If algavores are not keeping algae under control, it may be necessary to start a more aggressive regimen of water changes. One gallon every week or two gallons every two weeks should help reduce algae. A phosphate remover designed for reef aquariums may be necessary for particularly bad outbreaks. The photoperiod may also be reduced to discourage algae growth but this must be balanced with the needs of the animals containing photosynthetic zooxanthellae. There are a few "bad" organisms that may grow in a reef aquarium. One is Green Pearl algae (Valonia) which looks like green bubbles that grow directly on the live rock. Valonia will stress and possibly damage any cnidarians with which it comes into contact. In small numbers it is not harmful, but if the population of Valonia starts to increase, removal may be necessary. They can be removed from the rock with a pair of tweezers or deft fingers. Aiptasia anemones are another pest that can quickly grow out of control. They look like yellow polyps but are an ugly brown color and can grow much larger. Like their decorative cousins, Aiptasia uses powerful stinging cells to ward off neighbors and predators. In small numbers they will not pose a problem to the other animals in the tank, but if their rapid reproduction is unchecked, they can overcome a small aquarium quickly. The best way to avoid Aiptasia is to not purchase live rock that has them growing on it. Even so, a couple of hitchhikers are likely to reveals themselves after the reef is established. Unfortunately, they are rather difficult to remove. One strategy for removal is to grab them with a pair of pliers and pull as much off the rock as possible. This prevents them from reproducing for a while, but they are likely to grow back. Peppermint shrimp (Rhynchocinetes uritai) are reported to eat Aiptasia, but they will also eat decorative zoanthids. Other methods, like injecting them with vinegar or boiling water with a syringe, have also been suggested. A full-blown outbreak will probably require outside research and a little experimentation.

Outside of controlling problem algae and Aiptasia, stress in cnidarians is probably the most likely challenge in keeping a micro reef. Other animals living in the tank may stress Cnidarians. While the fish and crustaceans mentioned in this article are not likely to attack cnidarians, it’s always an outside possibility. If another animal is observed irritating or attacking a cnidarian regularly, you must make a decision whether to keep the stressed cnidarian or the guilty party. A photoperiod that is too long or too short may also cause stress. Shriveled cnidarians may appreciate a little less light for a period of time, followed by a gradual increase, so that they may adjust. Pale or weak-looking cnidarians may appreciate an increase in the photoperiod. Poor water quality will also cause stress in cnidarians. You may wish to periodically take a water sample in to an aquarium store for a broad-spectrum water test, especially if any of the animals appear to be struggling. If the results indicate a problem, initiate an aggressive water change regimen as described above. Finally, if nothing seems to work for a stressed cnidarian and it eventually dies, consider it a lesson learned and don’t try that particular animal again.


I hope this article inspires a few folks to venture into the wonderful world of marine reef keeping. Buyers beware, however; small reefs are known to be habit-forming and often turn into much larger ones! Since I started this article, Marineland has introduced a twelve-gallon Eclipse system that would be equally well suited to a simple micro reef, but will obviously cost more to set up and stock. Read as much as possible and don’t be afraid to ask questions, but keep in mind that there are as many opinions on the art of reef keeping as there are fish in the sea. Experience is the key and keeping a reef is the only way to gain it. Enjoy the micro reef; it will treat you to hours of fascination.


The Conscientious Marine Aquarist, by Robert Fenner
The Reef Aquarium, volumes one and two, by Charles Delbeek and Julian Sprung
Dr. Burgess’ Mini-Atlas of Marine Aquarium Fishes, by Warren Burgess et al.

This article first appeared in PVAS’s Delta Tale, Vol 31 # 2-3 & Vol 32, # 1