![Aquarium-Monaco1](https://upload.wikimedia.org/wikipedia/commons/0/0c/Aquarium-Monaco1.jpeg)
A reef aquarium or reef tank is a
marine aquarium
A marine aquarium is an aquarium that keeps ocean, marine plants and animals in a contained environment. Marine aquaria are further subdivided by hobbyists into fish only (FO), fish only with live rock (FOWLR), and reef aquarium, reef aquaria. Fi ...
that prominently displays live
coral
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...
s and other
marine invertebrates
Marine invertebrates are the invertebrates that live in marine habitats. Invertebrate is a blanket term that includes all animals apart from the vertebrate members of the chordate phylum. Invertebrates lack a vertebral column, and some have evo ...
as well as fish that play a role in maintaining the tropical
coral reef
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.
Co ...
environment. A reef aquarium requires appropriately intense lighting, turbulent water movement, and more stable water chemistry than fish-only marine aquaria, and careful consideration is given to which reef animals are appropriate and compatible with each other.
Components
Reef aquariums consist of a number of components, in addition to the livestock, including:
*Display tank: The primary tank in which the livestock are kept and shown.
*Stand: A stand allows for placement of the display tank at eye level and provides space for storage of the accessory components.
*Sump: An accessory tank in which mechanical equipment is kept. A remote sump allows for a clutter-free display tank.
*Refugium: An accessory tank dedicated to the cultivation of beneficial macroalgae and microflora/fauna. The refugium and sump are often housed in a single tank with a system of dividers to separate the compartments.
*Lighting: Several lighting options are available for the reef-keeper and are tailored to the types of coral kept.
*Canopy: The canopy houses the light fixtures and provides access to the tank for feeding and maintenance.
*Filtration and water movement: A variety of filtration and water movement strategies are employed in reef aquaria. Bulky equipment is often relegated to the sump.
Display tank
A "reef ready" or simply "drilled" tank is often used. This style of tank has holes drilled into the rear pane allowing water to drain into the sump or refugium.
These drains are usually housed in an internal overflow apparatus made of plastic or glass which encloses a drain standpipe and a water return line. The surface water pours over the overflow, down the standpipe, through
PVC piping, into the sump. After transiting the sump, water is pushed by a return water pump through the second hole and into the aquarium.
Alternatively, standard non-drilled aquariums employ an external "hang-on" overflow that feeds water via continuous
siphon
A siphon (from grc, σίφων, síphōn, "pipe, tube", also spelled nonetymologically syphon) is any of a wide variety of devices that involve the flow of liquids through tubes. In a narrower sense, the word refers particularly to a tube in a ...
to the sump.
The tanks are usually constructed from either glass or acrylic. Acrylic has the advantage of optical clarity, lightness, and ease of drilling. Drawbacks include a tendency to scratch easily, bowing, and often limited access from above due to top bracing. Glass aquariums are heavier but harder to scratch. Other materials such as epoxy-coated plywood have been used by industrious
DIY
"Do it yourself" ("DIY") is the method of building, modifying, or repairing things by oneself without the direct aid of professionals or certified experts. Academic research has described DIY as behaviors where "individuals use raw and semi ...
ers, but these materials are typically reserved for the construction of larger tanks.
Filtration
The primary biological filtration for reef aquariums usually comes from the use of
live rock
Live rock is rock from the ocean that has been introduced into a saltwater aquarium. Along with live sand, it confers to the closed marine system multiple benefits desired by the saltwater aquarium hobbyist. The name sometimes leads to misunders ...
which come from various tropical zones around existing reefs, or more recently
aquaculture
Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...
d rock from Florida. Some reefkeepers also use what is called
deep sand bed A deep sand bed is[How Sand Beds REALLY work](_blank)
by Ronald L Shimek, PhD, in s (DSB). These are often employed to augment the biological filtration by aiding in the reduction of
nitrate
Nitrate is a polyatomic ion
A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
, a waste product in an incomplete
nitrogen cycle
The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biologi ...
. Deep sand bed opponents may prefer a "bare bottom" or "suspended reef" which allows for easier removal of nitrate-generating accumulated detritus. This biological filtration is usually supplemented by
protein skimmer
A protein skimmer or foam fractionator is a device used to remove organic compounds such as food and waste particles from water. It is most commonly used in commercial applications like municipal water treatment facilities and public aquariums. Sm ...
s. Protein skimmers use the foam fractionation process wherein air is introduced into a water stream creating microbubbles. Organic waste adheres to the surface of these microbubbles and is removed as it overflows at the reactor surface into a removable cup. This group of elements used in conjunction is characteristic of the
Berlin Method, named for the city in which it was first devised.
In recent years the Berlin Method is often supplemented with a
refugium. A refugium provides many benefits, which include nitrate reduction, as well as providing a natural food source. It typically houses two main species of
macroalgae
Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of ''Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as k ...
, including ''
Caulerpa
''Caulerpa'' is a genus of seaweeds in the family Caulerpaceae (among the green algae). They are unusual because they consist of only one cell with many nuclei, making them among the biggest single cells in the world. A species in the Mediterran ...
prolifera'' or ''chaetomorphae'' or both (because these two strains are known not to spore but grow by rooting to propagate). Macroalgae is used for two reasons: to remove from the water excess nutrients such as nitrate, phosphate, and iron, and to support beneficial microflora and fauna (
zooplankton
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
). Small invertebrates (
copepod
Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...
s and
amphipod
Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descr ...
s) are provided a space free of predation to grow and, when returned to the display tank, serve as food for corals and fish. Conventional combined mechanical/biological filtration used in fish only systems is avoided because those filters trap
detritus
In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...
and produce nitrates which may stunt or even kill many delicate corals. Chemical filtration in the form of activated carbon is used when needed to remove discoloration of the water, or to remove dissolved matter (organic or otherwise) to help purify the water in the reef system.
Water movement
Water movement is important in the reef aquarium with different types of coral requiring different flow rates. At present, many hobbyists advocate a water turnover rate of 10x: 10 x aquarium capacity in gallons = required flow in gallons per hour—this is mathematically equivalent to a complete aquarium water turnover every 6 minutes. This is a general rule with many exceptions. Some corals, such as
mushroom corals and
polyp corals, require very little flow to thrive. Conversely, large-polyp
stony corals
Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a mo ...
such as
brain coral
Brain coral is a common name given to various corals in the families Mussidae and Merulinidae, so called due to their generally spheroid shape and grooved surface which resembles a brain. Each head of coral is formed by a colony of genetically ...
, bubble coral,
elegance coral
''Catalaphyllia'' is a monotypic genus of stony coral in the family Euphylliidae from the western Pacific Ocean. It is represented by a single species, ''Catalaphyllia jardinei'', commonly known as elegance coral (or wonder coral, ridge coral). I ...
, cup coral, torch coral, and trumpet coral require moderate amounts of flow, and small polyp stony corals such as ''
Acropora
''Acropora'' is a genus of small polyp stony coral in the phylum Cnidaria. Some of its species are known as table coral, elkhorn coral, and staghorn coral. Over 149 species are described. ''Acropora'' species are some of the major reef corals r ...
'', ''
Montipora
''Montipora'' is a genus of Scleractinian corals in the phylum Cnidaria. Members of the genus ''Montipora'' may exhibit many different growth morphologies. With eighty five known species, ''Montipora'' is the second most species rich coral genus ...
'', ''
Porites
''Porites'' is a genus of stony coral; they are small polyp stony (SPS) corals. They are characterised by a finger-like morphology. Members of this genus have widely spaced calices, a well-developed wall reticulum and are bilaterally symmetric ...
'', and
''Pocillopora'' require high, turbulent, conditions, which imitates breaking waves in shallow water near the tip of the reef. The directions which water pumps are pointed within an aquarium will have a large effect on flow speeds. Many corals will gradually move themselves to a different area of the tank if the water movement in its current area is not satisfactory.
"Since flow speed is the critical measure for determining the rate of gas exchange, turnover does little to convey how fast a coral will respire and photosynthesize."[Adams, Jake. "Water Flow is More Important for Corals Than Light, Part V." Advanced Aquarist V.6.1 (2007). http://www.advancedaquarist.com/2007/1/aafeature/view?searchterm=flow]
Reef ready tanks obtain at least a portion of the required water motion from the pump that returns water from the sump. This flow usually is augmented by other strategies. A popular strategy is placement within the display tank of multiple
powerheads. Powerheads are simply small submersible
water pumps
A pump is a device that moves fluids ( liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they ...
that produce a
laminar
Laminar means "flat". Laminar may refer to:
Terms in science and engineering:
* Laminar electronics or organic electronics, a branch of material sciences dealing with electrically conductive polymers and small molecules
* Laminar armour or "band ...
or narrow, unidirectional water stream. If the presence of the powerhead in the tank does not fit with the aesthetics of the display, small holes may be drilled in an overflow of a tank and the bulk of the powerhead can be hidden, leaving only the small funnel spout visible in the tank. The pumps may be alternately switched on and off using a wave timer and aimed at one another or at the aquarium glass to create
turbulent flow
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...
in the tank. Drawbacks to the use of these powerheads include their capacity to clutter the display tank, propensity for excess heat production, and the laminar quality of water flow often produced. Another method is the
closed loop in which water is pulled from the main tank into a pump which returns the water back into the aquarium via one or more returns to create water turbulence. Newer submersible
propeller
A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...
pumps are gaining popularity and are able to generate large volumes of turbulent water flow without the intensely directed laminar force of a power head. Propeller pumps are more energy-efficient than powerheads, but require a higher initial investment.
Another recent method is the gyre tank. A gyre tank encourages a maximum amount of water momentum through a divider in the center of the aquarium. The divider leaves an open, unobstructed space which provides a region with little friction against water movement. Building water momentum using a gyre is an efficient method to increase flow, thus benefiting coral respiration and photosynthesis.
Water flow is important to bring food to corals, since no coral fully relies on photosynthesis for food. Gas exchange occurs as water flows over a coral, bringing oxygen and removing gases and shedding material. Water flow assists in reducing the risk of thermal shock and damage by reducing the coral's surface temperature. The surface temperature of a coral living near the water's surface can be significantly higher than the surrounding water due to infrared radiation.
Lighting
With the advent of newer and better technologies, increasing intensities and a growing spectrum, there are many options to consider.
Many, if not most aquarium
coral
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...
s contain within their tissue the symbiotic algae called
zooxanthella
Zooxanthellae is a colloquial term for single-celled dinoflagellates that are able to live in symbiosis with diverse marine invertebrates including demosponges, corals, jellyfish, and nudibranchs. Most known zooxanthellae are in the genus ''Symbi ...
e. It is these zooxanthellae that require light to perform
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
and in turn produce simple sugars that the corals utilize for food. The challenge for the hobbyist is to provide enough light to allow photosynthesis to maintain a thriving population of zooxanthellae in a coral tissue. Though this may seem simple enough but in reality can prove to be a very complex task.
Some corals, such as
mushroom corals and
polyp corals, require very little light to thrive. Conversely, large-polyp
stony corals
Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a mo ...
such as
brain coral
Brain coral is a common name given to various corals in the families Mussidae and Merulinidae, so called due to their generally spheroid shape and grooved surface which resembles a brain. Each head of coral is formed by a colony of genetically ...
, bubble coral,
elegance coral
''Catalaphyllia'' is a monotypic genus of stony coral in the family Euphylliidae from the western Pacific Ocean. It is represented by a single species, ''Catalaphyllia jardinei'', commonly known as elegance coral (or wonder coral, ridge coral). I ...
, cup coral, torch coral, and trumpet coral require moderate amounts of light, and small polyp stony corals such as ''
Acropora
''Acropora'' is a genus of small polyp stony coral in the phylum Cnidaria. Some of its species are known as table coral, elkhorn coral, and staghorn coral. Over 149 species are described. ''Acropora'' species are some of the major reef corals r ...
'', ''
Montipora
''Montipora'' is a genus of Scleractinian corals in the phylum Cnidaria. Members of the genus ''Montipora'' may exhibit many different growth morphologies. With eighty five known species, ''Montipora'' is the second most species rich coral genus ...
'', ''
Porites
''Porites'' is a genus of stony coral; they are small polyp stony (SPS) corals. They are characterised by a finger-like morphology. Members of this genus have widely spaced calices, a well-developed wall reticulum and are bilaterally symmetric ...
'', and
''Pocillopora'' require high intensity lighting.
Of the various types, most popular aquarium lighting comes from
metal halide lamp
A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
s, very high output or VHO,
compact fluorescent
A compact fluorescent lamp (CFL), also called compact fluorescent light, energy-saving light and compact fluorescent tube, is a fluorescent lamp designed to replace an incandescent light bulb; some types fit into light fixtures designed for inca ...
and
T5 high output lighting systems. Although they were once widely used, many reef tank aquarists have abandoned T12 and T8 fluorescent lamps due to their poor intensity, and
mercury vapor due to its production of a limited
light spectrum
The electromagnetic spectrum is the range of frequency, frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energy, photon energies.
The electromagnetic spectrum covers electromagnetic waves with f ...
.
Recent advances in lighting technology have also made available a completely new technology for aquarium lighting:
light emitting diodes
A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
(LEDs). Although LEDs themselves are not new, the technology has only recently been adapted to produce systems with qualities that allow them to be considered viable alternatives to gas- and filament-based aquarium lighting systems. The newness of the technology does cause them to be relatively expensive, but these systems bring several advantages over traditional lighting. Although their initial cost is much higher, they tend to be economical in the long run because they consume less power and have far longer lifespans than other systems. Also, because LED systems are made of hundreds of very small bulbs, a microcomputer can control their output to simulate daybreak and sunset. Some systems also have the ability to simulate moonlight and the phases of the moon, as well as vary the
color temperature
Color temperature is the color of light emitted by an idealized opaque, non-reflective body at a particular temperature measured in kelvins. The color temperature scale is used to categorize the color of light emitted by other light sources ...
of the light produced. Moreover, some manufacturers produce LED lighting systems in single bright and double bright intensities for sustaining coral life in marine aquariums.
The choices for aquarium lighting are made complicated by variables such as color temperature, (measured in
kelvin
The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and phys ...
s),
color rendering index
A color rendering index (CRI) is a quantitative measure of the ability of a light source to reveal the colors of various objects faithfully in comparison with a natural or standard light source. Light sources with a high CRI are desirable in ...
(CRI),
photosynthetically active radiation Photosynthetically active radiation (PAR) designates the spectral range (wave band) of solar radiation from 400 to 700 nanometers that photosynthetic organisms are able to use in the process of photosynthesis. This spectral region corresponds more o ...
(PAR) and
lumens. Power output available to the hobbyist can range from a meager 9 W
fluorescent
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
lamp to a blinding 1000 W metal halide lamp. Lighting systems also vary in the light output produced by each bulb type—listed in order of weakest to strongest they would be: T8/12 or normal output lamps, compact fluorescent and T5 high output, VHO, and metal halide lamps. To further complicate matters, there are several types of
ballast
Ballast is material that is used to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within a boat, ship, ...
s available: electric ballast, magnetic ballast, and pulse start ballast.
Heating and cooling
Reef tanks are usually kept at a temperature between 25 and 28 °C (75–82 °F). Radical temperature shifts should be avoided as these can be particularly harmful to reef invertebrates and fish. Depending on the location of the tank and the conditions therein (i.e. heat/air conditioning), one may install a heater and/or a chiller for the tank. Heaters are relatively inexpensive and readily available at any local fish store. Aquarists frequently use the sump to hide unsightly equipment such as heaters. Chillers, on the other hand, are expensive and are more difficult to locate. For many aquarists, installing surface fans and running home air conditioning suffice in place of a chiller. Fans cool the tank via evaporative cooling and require more frequent top-off of the aquarium water.
Water chemistry
Stony corals, which are defined by their calcareous calcium carbonate skeletons (CaCO
3), are the focus of many advanced reef keepers. These corals require additional attention to water chemistry, especially maintenance of stable and optimal calcium, carbonate, and pH levels. These parameters may be tracked and adjusted with test kits and frequent manual dosing of calcium and pH buffer additives requiring no additional equipment. Alternatively, automated methods employing small dedicated computers with electronic water quality monitoring capabilities are often used to control water chemistry parameters via several components including calcium reactors and kalkwasser reactors. Calcium reactors are canisters filled with crushed coral skeletons. Carbon dioxide is injected into the canister acidifying the water and dissolving the coral skeletons. The acidified and CaCO
3 rich solution is then pumped into the sump. The excess CO
2 then diffuses out of the water and into the air leaving behind the CaCO
3. Kalkwasser is an aqueous solution of calcium hydroxide, Ca(OH)
2. The kalk reactor stirs and dispenses the solution into the sump where the Ca(OH)
2 combines with dissolved CO
2 to produce CaCO
3. These components must be controlled by a computer to prevent dangerous changes in pH due to the acidic calcium reactor effluent or alkaline kalkwasser effluent.
Optimal water parameters are:
*
Salinity
Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
: 1.022–1.025
sg or 30–34 parts per thousand (ppt)
*Temperature: 24–27 °C (76–80 °F)
*
Ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
(NH
3): 0 parts per million (ppm)
*
Nitrite
The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...
(NO
2−): 0 ppm
*
Nitrate
Nitrate is a polyatomic ion
A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
(NO
3−): 0–10 ppm
*
Phosphate
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid .
The phosphate or orthophosphate ion is derived from phospho ...
(PO
43−): 0–0.06 ppm
*
pH: 8.2–8.6
*
Calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
(Ca
2+): 400–450 ppm
*
Alkalinity
Alkalinity (from ar, القلوي, al-qaly, lit=ashes of the saltwort) is the capacity of water to resist acidification. It should not be confused with basicity, which is an absolute measurement on the pH scale.
Alkalinity is the strength of ...
: 7–12 dKH
Trace elements can become depleted by marine livestock and filtration, and can be replenished during a water change.
Safety
Large volumes of electrically conductive salt water, complex plumbing, and numerous electrical appliances housed in close proximity certainly pose a significant risk of damage to both person and property and require close attention to safety. All equipment should be used according to manufacturer instructions. Electrical equipment should be placed above water level whenever possible, and drip loops should always be used. Circuit limits should never be exceeded and all appliances should be plugged into
ground fault circuit interrupter
A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) is an electrical safety device that quickly breaks an electrical circuit with leakage current to ground. It is to protect equip ...
(GFCI) outlets. These can be purchased at any hardware store and are relatively easy to install. Plug in GFCI power strips are also readily available. Home monitoring equipment with water sensors can also be adapted for the home aquarist and used to alert the owner of power outages or water overflows. This equipment can allow for timely intervention in a potential disaster and provides an added sense of security for frequent travelers.
Nano reefs
![3 gallon pico reef](https://upload.wikimedia.org/wikipedia/commons/5/51/3_gallon_pico_reef.jpg)
A nano reef is a type of
marine aquarium
A marine aquarium is an aquarium that keeps ocean, marine plants and animals in a contained environment. Marine aquaria are further subdivided by hobbyists into fish only (FO), fish only with live rock (FOWLR), and reef aquarium, reef aquaria. Fi ...
that is typically less than 140 litres (30 Imperial gallons / 37 US gallons). The exact limit that distinguishes a nano reef from a regular reef is somewhat ill-defined. Some claim that anything less than 180 litres (40 Imperial gallons / 48 US gallons) would qualify. But 140 litres (30 Imperial gallons / 37 US gallons) seems to be the generally accepted limit. Nano reefs have become quite popular in recent years among fish keeping hobbyists, primarily because of their smaller size, maintainability, and the possibility of lower costs. The burgeoning interest in this niche of marine aquarium science has fostered several notable contributions ranging from specific consumer products such as specialized aquarium filters, compact high intensity lighting systems and smaller circulation pumps. Such equipment allows the aquarist to maintain an environment wherein many marine organisms are capable of thriving.
The first reference to these small reef aquariums was made in 1989 by Albert J. Thiel in his book ''Small Reef Aquarium Basics''.
Nano reefs are very commonly sold as complete kits which contain the tank, stand, power compact T5, T8, PL lamps or
metal halide lighting
A metal-halide lamp is an electrical lamp that produces light by an electric arc through a gaseous mixture of vaporized mercury (element), mercury and metal halides (compounds of metals with bromine or iodine). It is a type of high-intensity d ...
, protein skimmer, UV steriliser, 3 or more stage filtration, a heater and a water pump or powerhead. However, many nano reefkeepers decide to upgrade their aquariums with better quality equipment such as a more powerful protein skimmer or lighting.
Pico reefs
Another term gaining popularity is ''pico reef'', which is used to refer to the smallest of nano reef aquariums. Most online forum polls set the range of approximately 10 litres (2.5 gallons) and below as pico reefs. These tiny tanks require even more diligence with regard to water changes and attention to water chemistry because the small water volume provides little room for error. Care must be exercised when stocking these tiny tanks because too many inhabitants can easily overload the tank's ability to process wastes effectively. For the smallest of pico reefs, even the presence of a single fish is discouraged. Pico reefs often consist of
live rock
Live rock is rock from the ocean that has been introduced into a saltwater aquarium. Along with live sand, it confers to the closed marine system multiple benefits desired by the saltwater aquarium hobbyist. The name sometimes leads to misunders ...
, hardy corals, and small invertebrates such as
hermit crab
Hermit crabs are anomuran decapod crustaceans of the superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit crab, most of which possess an a ...
s and marine snails. The keeping of pico reef aquariums has tested the extent of
allelopathy
Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the germination, growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have be ...
, the chemical and physical means by which corals compete for space. Before the advent of these concentrated environments, it was thought to be impossible for corals of even a few mixed genera to occupy such a small shared water volume.
[''The history of pico reef biology.'']
/ref>
Challenges associated with small reef aquariums
Due to the small water volume, fluctuations of water quality occur more easily, and so nano reef aquariums require extra attention to water quality compared to aquariums of larger water volumes. Many experienced reef aquarists recommend testing the water twice weekly, with water changes at least every week. In particular, ammonia, nitrite, nitrate, pH, salinity, alkalinity, calcium and phosphate levels should be monitored closely. When it comes to nano reefs, even minute changes in water conditions such as mild temperature fluctuations can be problematic, whereas the greater water volume of larger aquariums provides a more stable and flexible environment.
Nano reefs also require extra care in the selection of occupants. There are two major factors to be considered: biological load, i.e., the ability of the tank to process the wastes produced by the occupants, and species compatibility. These issues, though present in larger tanks, are magnified in the nano tank. Species considered reef safe
Reef safe is a distinction used in the saltwater aquarium hobby to indicate that a fish or invertebrate is safe to add to a reef aquarium. There is no fish that is completely reef safe. Every fish that is commonly listed as reef safe are species th ...
and able to coexist in larger tanks may not do well in a nano tank because of their close physical proximity. For this reason, smaller species of fish, such as gobies
Gobiidae or gobies is a family of bony fish in the order Gobiiformes, one of the largest fish families comprising more than 2,000 species in more than 200 genera. Most of gobiid fish are relatively small, typically less than in length, and the ...
and clownfish
Clownfish or anemonefish are fishes from the subfamily Amphiprioninae in the family Pomacentridae. Thirty species of clownfish are recognized: one in the genus ''Premnas'', while the remaining are in the genus ''Amphiprion''. In the wild, th ...
, are popular choices because of their relatively small size and ability to coexist peacefully with other tank inhabitants.
Filtration in nano reefs
Many nano reef aquarists prefer their displays to be as natural-looking as possible, and therefore choose to use as few mechanical filtration methods as possible. A primary filtration method in nano reefs is live rock
Live rock is rock from the ocean that has been introduced into a saltwater aquarium. Along with live sand, it confers to the closed marine system multiple benefits desired by the saltwater aquarium hobbyist. The name sometimes leads to misunders ...
and live sand Live sand, a term used in aquarism, is natural reef coral sand populated with millions of beneficial bacteria and organisms which aid in the dissolving of organic wastes like ammonia, nitrites and nitrates produced by larger organisms in saltwater ...
, which are pieces of rock and sand that have broken from the coral reef
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.
Co ...
and are populated with beneficial bacteria and other organisms that aid in breaking down organic wastes produced by larger organisms in the nano reef. Other nano reef aquarists use devices such as protein skimmer
A protein skimmer or foam fractionator is a device used to remove organic compounds such as food and waste particles from water. It is most commonly used in commercial applications like municipal water treatment facilities and public aquariums. Sm ...
s to remove excess waste from the aquarium, before it has a chance to be broken down to nitrate. Removing the excess wastes mechanically can reduce the frequency of water changes needed to keep nitrate levels low. Delaying the action of the mechanical filters, such as by means of a day-night timer, can allow invertebrates to filter-feed naturally. A refugium may also be used to export nutrients, when packed with macroalgae
Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of ''Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as k ...
such as ''Chaetomorpha
''Chaetomorpha'' is a genus of green algae in the family Cladophoraceae.Guiry, M. D. (2004)''Chaetomorpha''.''In:'' Guiry, M. D. & Guiry, G. M. (2017). AlgaeBase. Accessed through: World Register of Marine Species on 9 August 2017. Members of thi ...
'', and live rock. Deep sand bed filters are another filtration method.
Recently there have been several "natural" methods of processing waste in the aquarium and specifically small environments as nano-reefs. The research on the encouragement of the development of different types of sponges and micro-organisms to process the pollutants in the aquarium, a matter that has been gaining popularity in the aquarium community.
Livestock
Fish
* Angelfish
*Blennies
Blenny (from the Greek and , mucus, slime) is a common name for many types of fish, including several families of percomorph marine, brackish, and some freshwater fish sharing similar morphology and behaviour. Six families are considered "true ...
*Butterflyfish
The butterflyfish are a group of conspicuous tropical marine fish of the family Chaetodontidae; the bannerfish and coralfish are also included in this group. The approximately 129 species in 12 genera are found mostly on the reefs of the Atlant ...
es
*Cardinalfish
Cardinalfishes are a family, Apogonidae, of ray-finned fishes found in the Atlantic, Indian, and Pacific Oceans; they are chiefly marine, but some species are found in brackish water and a few (notably ''Glossamia'') are found in fresh water. A h ...
*Clownfish
Clownfish or anemonefish are fishes from the subfamily Amphiprioninae in the family Pomacentridae. Thirty species of clownfish are recognized: one in the genus ''Premnas'', while the remaining are in the genus ''Amphiprion''. In the wild, th ...
*Damselfish
Damselfish are those within the subfamilies Abudefdufinae, Chrominae, Lepidozyginae, Pomacentrinae, and Stegastenae within the family Pomacentridae. Most species within this group are relatively small, with the largest species being about 30 ...
es
*Eel
Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 19 families, 111 genera, and about 800 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...
s
* Gobies
Gobiidae or gobies is a family of bony fish in the order Gobiiformes, one of the largest fish families comprising more than 2,000 species in more than 200 genera. Most of gobiid fish are relatively small, typically less than in length, and the ...
* Grammas
*Rabbitfish
Rabbitfishes or spinefoots are perciform fishes in the family Siganidae. The 29 species are in a single genus, ''Siganus''. In some now obsolete classifications, the species having prominent face stripes—colloquially called foxfaces– ...
*Tangs
TANGS is a department store located on Orchard Road in Singapore, owned by C.K. Tang Limited. The store is regarded as a principal shopping destination in the city, comparable to Bloomingdale's in New York City and Selfridges
Selfridges, a ...
Invertebrates
* Candycane coral ('' Caulastrea furcata'')
* Frogspawn coral (''Euphyllia divisa
Euphyllia divisa (reclassified in 2017 as Fimbriaphyllia divisa), commonly known as frogspawn coral and sometimes misspelled ''Euphyllia divisia'', is a large-polyped stony coral native to the Indo-Pacific islands. It is a commonly kept species ...
'')
* Hammer coral ('' Euphyllia ancora'')
* Pulse coral ( ''Heteroxenia sp.'')
* Brain coral
Brain coral is a common name given to various corals in the families Mussidae and Merulinidae, so called due to their generally spheroid shape and grooved surface which resembles a brain. Each head of coral is formed by a colony of genetically ...
* Button polyp ( ''Zoanthus sp.'')
* Star polyp (''Briareum violaceum
''Briareum violaceum'', commonly called star polyp, is a species of a soft coral
Alcyonacea, or soft corals, are an order of corals. In addition to the fleshy soft corals, the order Alcyonacea now contains all species previously known as "go ...
'')
* Sun coral ''( Tubastraea sp.)''
* Cleaner shrimp
Cleaner shrimp is a common name for a number of swimming decapod crustaceans, that clean other organisms of parasites. They belong to any of three families, Hippolytidae (including the Pacific cleaner shrimp, ''Lysmata amboinensis''), Palaem ...
* Turbo snail
*Linckia
''Linckia'' is a genus of sea stars found mainly in the Indo-Pacific region. They are known to be creatures with remarkable regenerative abilities, and capable of defensive autotomy against predators. They reproduce asexually.
The genus is name ...
sea stars
References
External links
*
RTAW Reefpedia
a Reef Keeping wiki maintained by th
Marine Aquarium Societies of Australia
{{Aquarium
Fishkeeping
Fisheries science