Glossary of Aquarium / Fish keeping Terms

A.R.M.		Aragonite Reactor Media
Absorption		The process of retaining one substance within another without any chemical or physical interaction (bonding)–in contrast to adsorption. A sponge absorbs water as the water does not bind to the sponge and is easily reclaimed by squeezing the sponge.
AC		See Activated carbon
Acclimation		A change that occurs in an organism to allow it to tolerate a new environment. The process of preparing an organism to be introduced to a new aquarium safely.
Acidity		Is when water has a low pH < 7 heading down to 1. The lower the number the higher the acidity. High acidity will kill most fish and invertebrates.
Acropora		A genus of hard (stony) corals that contain the elkhorn and staghorn corals.
Acrylic		A form of plastic that has uses much like glass. Acrylic is stronger than glass, and can be bent at various angles. Acrylic pieces are chemically bonded together. The downside is that acrylic is easily scratched.
Activated Carbon		Is a highly adsorbent carbon-based material used as a chemical filter media. Activated carbon adsorbs dissolved organics such as tannins and phenols from the water. Activated carbon does not remove ammonia, nitrite or hardness causing compounds. It is made from a variety of materials such as bituminous and lignite coal, coconut shells, peat and wood. Bituminous coal based carbons are the best choice for aquarium water filtration as they are hard, have a large internal surface area and the widest range of pore sizes.
Aerobic		Two uses in the hobby. When referring to bacteria (as in aerobic bacteria), it means bacteria which can live or grow only where free oxygen is present. In a more general usage (an aerobic environment), it means an area where free oxygen is present. The opposite of anaerobic.
AF		Auto Feeder
AFS		Automatic Feed System
AGA		All-Glass Aquarium
Aiptasia		Small pest anemones that will retract into crevices or holes in rock-face when threatened. Not reef safe. Will spread quickly. Around 1-3 inches, from a white-pink-brown coloration.
Air Pump		Mechanical device that compresses air and forces it into your aquarium, via flexible tubing. Used to run air stones, under-gravel filters, or decorations and create air bubbles that add oxygen to aquarium water.
Algae		Unicellular, multicellular, solitary, or colonial organisms that contain chlorophyll. They lack roots, stems, leaves, flowers, and seeds. Algae are in the Kingdom Protista. Many types of algae are common in reef aquariums, some are desirable while others are considered pests.
Algal Bloom		A sudden spurt of algal growth that can indicate potentially hazardous changes in aquarium water chemistry.
Alk		Alkalinity, measure of buffering capacity of water
Alkaline		Having a pH of more than 7. Alkaline solutions are also said to be basic.
Alkalinity		A measure of the acid-neutralizing capacity (ANC) of water. Acid-neutralizing capacity means the ability to accept acid without a subsequent drop in pH. The more acid that can be added to water before the pH starts to drop, the higher the alkalinity.
Ammonia		NH3, a toxic substance that builds up in the aquarium. It is released by fish through their gills and as a result of waste buildup. Ammonia is the first step in the nitrogen cycle, and is removed by bacterial action where it is transformed into nitrite.
Anaerobic		Two uses in the hobby. When referring to bacteria (as in anaerobic bacteria), it means bacteria which can live or grow where free oxygen is not present. In a more general usage (an anaerobic environment), it means an area where free oxygen is not present. The opposite of aerobic.
ANGFA		Australia New Guinea Fishes Association
Anions		Elements or compounds (groups of elements) that have a negative charge. The negative charge is a result of having gained one or more electrons. Orthophosphate (PO43-), nitrite (NO2-), nitrate (NO3-), chloride (Cl-) and sulfate (SO42-) are common anions in aquarium water.
Antibiotics		A type of medication generally used to kill or inhibit the growth of bacteria.
AP		See Air Pump
API		Aquarium Pharmaceuticals Inc
Apoptosis		Programmed cell death
Aquaculture		The growing of aquatic organisms in controlled environments for any commercial, recreational, or public purpose; sector of fisheries that includes the rearing or raising under controlled conditions of aquatic products such as fishes, mollusks, crustaceans, sea weeds and other aquatic resources. In the aquarium industry aquaculture is most commonly used to grow out coral fragments or breed ornamental fish.
Aquascape		Contraction of “aquarium landscape.” Refers to the overall physical design and layout of the aquarium interior including rock, plants, and accessories.
Aragonite		A calcareous substrate or sand. It’s commonly used as a sand bed in reef aquariums, and is available in various grain sizes.
ARAZPA		Australasian Regional Association of Zoological Parks and Aquaria
Arthropoda		An animal phylum that contains lobsters, crabs, shrimp, mantis shrimp, barnacles and copepods, fairy shrimp (all crustaceans), insects, centipedes, millipedes, spiders, scorpions, horseshoe crabs, pycnogonids (sea spiders), ticks and mites. Approximately three quarters of a million species are described, many more than all the other animal phyla combined. The crustaceans are the arthropods associated with coral reefs.
ATM		Acrylic Tank Manufacturing
ATO		Automatic Top Off
ATS		Algae Turf Scrubber
ATS		Algae turf scrubber, reef setup technique
ATU		Auto Top-Up
Autotrophic Bacteria		Bacteria whose carbon needs for growth and reproduction are fulfilled by carbon dioxide. Autotrophy refers to the carbon source, not the energy source for growth. Autotrophic bacteria are in contrast to heterotrophic bacteria. The nitrifying bacteria, Nitrosomonas and Nitrobacteria are autotrophic bacteria. They obtain energy by oxidizing inorganic compounds, ammonia or nitrite, respectively (see lithotrophic), while reducing carbon dioxide
BB		Bare Bottom
BBA		Black Brush Algae
Berlin System		A method of biological filtration that uses only live rock and a powerful protein skimmer.
BF		Biological Filter
Biological Filtration		Is the natural process of beneficial bacteria breaking down harmful ammonia to nitrite and then converting nitrite to less toxic nitrate. A biological filter is a physical structure or device designed to promote nitrification. Biological filtration is the most important of the three types of aquarium filtration (the others being mechanical and chemical filtration). Types of biological filters include trickle filters, wet/dry filters, Bio-Wheels, and under-gravel filters.
Biological Filtration		A method of natural filtration that uses bacteria to break down waste substances by means of the nitrogen cycle. Examples such as live rock, trickle filters, bio-wheels, and sponge filters.
Bleaching		Loss of zooxanthellae in corals with resultant white coloration caused by a bacterial infection or environmental stress.
BOD		Biological oxygen demand
Brackish		Mixed fresh and salt water.
BT		Blue Tang
BTA		Bubble Tip Anemone
Buffer		a substance that can neutralize a base or an acid so that the original pH of the liquid is maintained or changes much more slowly than if the buffer were not present. Acidity and alkalinity are two measurement of buffering capacity.
CA		Coralline Algae
Ca		Calcium
Ca(OH)2		Calcium hydroxide
CA3		Carbonic anhydrase 3
CaCl2		Calcium chloride
CaCO3		Calcium carbonate
Calcareous		Composed of or containing a substance made of calcium carbonate.
Canister Filter		versatile, large capacity external filtration device located below the aquarium. An integrated water pump pulls water through layers of customizable filter media and returns clean water to the aquarium via hoses.
Carbon dioxide (CO₂)		a colorless, odorless gas which readily dissolves in water to form carbonic acid. Carbon dioxide is respired by animals, absorbed by plants during photosynthesis, and produced by heterotrophic bacteria during mineralization of organic material.
Carnivore		organism that almost exclusively feeds on animals.
Cations		elements or compounds (groups of elements) that have a positive charge. A significant portion of the ammonia in water is in the cation form called ammonium (written NH4+). Calcium (Ca2+), magnesium (Mg2+), sodium (Na+), and potassium (K+) are other common cations in aquarium water.
CB		Calcium Buffer
CBB		Copper Band Butterfly
CBS		Coral Banded Shrimp
CBS		Crystal Black Shrimp
CC		Crushed Coral
CC		Counter current, type of protein skimmer
CCAP		Culture Collection of Algae and Protozoa
CF		See Canister Filter/ Cartridge Filters
CH		Carbonate hardness
Chaeto		Chaetomorpha or “Chaeto” algae is a green macro algae from the Division Chlorophyta and is one of the more common plants to keep in your marine aquarium to help maintain your water purity. The most common species is Chaetomorpha linum and is probably what is in your tank.
Chemical Filtration		the removal of dissolved substances by chemically or physically binding them to filter media such as activated carbon. Other types of chemical filtration media are ion exchange resins and clinoptilolite.
Chemolithoautotrophic Bacteria		bacteria which live (-trophic) by obtaining their energy from chemical reactions (chemo-), their carbon from carbon dioxide (auto-), and their electron donor chemically (litho-). The nitrifying bacteria, Nitrosomonas and Nitrobacter, are chemolithoautotrophic bacteria.
Chiller		A piece of equipment used to cool down the water in an aquarium. Chillers are available in different types and sizes, including one that hooks up in-line with the water flow of the tank and one that drops into the sump. They all feature a thermostat for maintaining a constant temperature. Larger tanks require larger chiller units. These are generally used when the water temperature cannot be kept below 82°F by itself.
Chloramine		chemical compound of chlorine and ammonia used to treat municipal water, often as an alternative to chlorine. Harmful to aquarium inhabitants.
Cl		Chlorine
Clinoptilolite		a type of zeolite which has a demonstrated affinity for certain cations such as ammonia. Used as a chemical filtration media in the aquarium hobby. Most common use is as cat litter.
CO2		See Carbon dioxide
CO2 System		series of devices assembled to introduce and regulate carbon dioxide for aquarium use. Often used to supplement CO₂ levels to encourage lush plant growth. Also, a vital component of a calcium reactor.
CO3		Carbonate
Community Tank		an aquarium populated with fish of several different species, all of which are compatible with one another. They may originate from different regions of the world but are able to be housed together since they share similar water parameter requirements.
Compound		substance combining two or more elements from the periodic table of elements.
Coralline Algae		Algae that form solid calcium carbonate accretions. Coralline is desirable in reef aquariums, and helps prevent undesirable algae from growing. Covers rocks, aquarium walls, and equipment. Usually pink or purple, turns white when it dies.
CP		Circulation Pump
CPD		Celestial Pearl Danio
CR		Calcium Reactor
CRS		Crystal Red Shrimp
Crustacean		A sub phylum of Arthropoda that includes shrimp, mantis shrimp, lobsters, crabs, water fleas, copepods, crayfish and wood lice. There are almost 40,000 described species of crustaceans. The Crustacea are mainly aquatic, but include some semi-terrestrial and terrestrial groups.
CTA		Cellulose triacetate, type of RO membrane
Cu		Copper
CUC		Clean Up Crew
Cyano		Cyanobacteria: A photosynthetic aquatic bacteria, often called blue-green algae, but have no relationship to algae. Not all “blue-green” bacteria are blue; some common forms are red or pink. In an aquarium environment cyanobacteria can quickly cover and kill corals.
Cycling		a process of establishing biological filtration in an aquatic system by promoting the growth of nitrifying bacteria.
DC		Direct current
DD		Downdraft, type of protein skimmer
De-ionization		A water purification method, typically used in conjunction with reverse osmosis purification.
Denitrification		a chemical reduction process in which nitrate is converted (reduced) to dinitrogen gas by bacterial processes. Denitrification is an anaerobic process which can eliminate nitrate from water. There are a number of intermediate steps which form compounds such as nitrous oxide (N2O). Denitrification is carried out by bacteria such as Pseudomonas, Alcaligenes, and Rhodopseudomonas.
Detritivores		An organism that feeds on dead organic material, detritus.
Detritus		Waste or debris of any kind. Organic matter produced by the decomposition of organisms.
DHA		Docosahexaenoic Acid (omega-3 fats)
DHG		Dwarf Hair Grass
DI		Deionisation, type of water purification
Dinoflagellate		Is a single-celled organism with two flagella, occurring in large numbers in marine plankton and also found in fresh water. Some produce toxins that can accumulate in shellfish, resulting in poisoning when eaten. These plants are tiny single-celled algae, the zooxanthellae or symbiotic dinoflagellates, that live within the tissues of corals in great numbers.
Dissolved Organic Carbon		includes a variety of carbon based (thus organic) compounds that are dissolved in water. They are in contrast to particulate material. Tannins and phenols are two common DOCs in aquarium water. Studies have shown that increased levels of DOC inhibit nitrification. DOC is produced by several processes including biodegradation.
DIY		Do it yourself
dKH		Degrees of carbonate hardness, measure of alkalinity
DO		Dissolve oxygen
DOC		Dissolved organic carbon
DOS		Dissolved organic solids
Doser		a liquid distribution system, either gravity-fed or mechanically pumped, used to maintain aquarium water levels. They can also be used to add a controlled supply of additives, such as kalkwasser, or trace elements to your system.
DP		See Doser
DSB		Deep Sand Bed. Generally 100mm or deeper.
DT		Display Tank
EPA		Eicosapentaenoic Acids (omega-3 fats)
FB		Fluidized Bed
FBF		Fluidized Bed Filter
Fe		Iron
FF		Filter Floss
FO		Fish Only
FOWLR		Fish-Only-With-Live-Rock
Frag		A fragment of a parent coral, or small coral. See Fragmentation.
Frag Plug		A small disc or cylinder made of ceramic, aquarium substrate, rubble rock, etc. used to mount coral frags on. Often made to fit into holding racks for coral grow-out.
Fragmentation		A means of artificial reproduction by which sections or segments of a coral is divided, cut, or broken into pieces from which a new colony is grown.
Fry		recently hatched fish.
FSB		Fluidized Sand Bed
FT		Fish Tank
FW		Freshwater
GBR		Great Barrier Reef
GBTA		Green Bubble Tip Anemone
GDA		Green Dust Algae
GH		General Hardness
GHA		Green Hair Algae
GPH		Gallons per hour
GSA		Green Spot Algae
GSP		Green Star Polyps
HA		Hair Algae
HCO3		Hydrogen carbonate
Herbivore		organism whose diet consists mainly of vegetable matter.
Heterotrophic Bacteria		Bacteria which utilize organic compounds for their carbon and energy needs. Heterotrophic bacteria are responsible for the mineralization, or degradation of uneaten food, plant material, dead organisms and the other organic based matter that accumulates in an aquarium. Their processes are responsible for recycling nutrients and minerals.
HG		Hair Grass
HO		High output fluorescent light
HOB		Hang-On-Back
HOG		Hang-On-Glass
HOT		Hang on Tank
HUFA		Highly Unsaturated Fatty Acids (omega-3 fats)
Hydrometer		A device used to measure the specific gravity of seawater. The most common types consist of a clear chamber with a floating needle.
Hypoxia		Lacking or deficient in oxygen
I		Iodide
I2		Iodine
IAL		Indian Almond Leaf
Ichthyology		The branch of zoology devoted to the study of fish.
Ick		Cryptocaryon Irritans Paracite (or ich) a very common parasitic disease characterized by white, salt-like specks all over the fish.
Internal Filter		a filter operated completely inside the tank, either fully or partially submerged. Examples include under-gravel and sponge filters, which cultivate beneficial bacteria for biological filtration. Internal power filters provide superior 3-stage filtration.
Invertebrate		Animals with no backbones. This group includes mollusks, crustaceans, worms, corals, and composes a large number of reef inhabitants.
IO3		Iodate
Ion Exchange		a type of filtration whereby one ionized compound (or element) changes places with another on the surface of a media. The media can be a natural occurring (e.g. clinoptilolite) or man-made such as ion exchange resins. Common uses for ion exchange media include: removing hardness from water (the calcium and magnesium in the water are exchanged for sodium on the media) and ammonia removal by exchange also with sodium. De ionization (DI) water systems use ion exchange media to purify water by removing cations and anions by exchanging them with hydrogen and hydroxyl ions, respectively.
Ions		elements or compounds (groups of elements) that have a negative or positive charge because of having gained or lost one or more electrons. See also anions and cations.
IR		Infrared
Jararrium		is a “Self-Sustaining Ecosystem”
Kalkwasser		A solution of calcium hydroxide in water, which is alkaline. Also known as limewater. An additive that is slowly dripped into a reef aquarium to raise the alkalinity and calcium levels.
KI		Potassium iodide
LFS		Local Fish Shop
Light Meter		precision instrument that measures light intensity. It is the most accurate way to gauge how much light your aquarium inhabitants actually receive. This is especially important for photosynthetic corals.
Lithotrophic Bacteria		bacteria which get their energy for growth from inorganic compounds such as ammonia, nitrite or nitrate.
Live-bearer		any fish that gives birth to live young, such as Guppies, Platies, Mollies and Swordtails.
LPS		Large polyped Scleractinian (stoney) coral
LR		Live rock
LTA		Long Tentacle Anemone
Macroalgae		Large plant-like algae commonly found in red, green and brown varieties. One of the most common of these is Caulerpa, which produces large green spheres resembling grapes.
MASA		Marine Aquarium Societies of Australia
Mechanical Filtration		the trapping of particulate material from aquarium water by straining the water through a pad, sponge, or similar media, and the subsequent removal and cleaning of that media. This process reduces water turbidity and removes particulate organic material from the system. Mechanical filtration should be placed before chemical and biological filtration as it helps prevent the clogging of the media of these two types of filtration processes.
MEQ/L		Milli-equivalents per litre, measure of alkalinity
Mg		Magnesium
MH		Metal halide light
Micron (um)		is a unit of measurement. When measuring lengths < 1 milliliter. 1mm = 1000micron (um)
Mineralization		is the breakdown of organic matter by bacteria into inorganic compounds such as ammonia and carbon dioxide.
MM		Miracle Mud
Molecular		the smallest form of an element or compound that can exist in the free state (without a charge). NH3 is the molecular form of ammonia.
MTS		Multiple Tank Syndrome
Na		Sodium
NaCO3		Sodium carbonate
Nano Reef		A small reef aquarium, generally 20 gallons or less. Also known as nanoreef or nano-reef.
NaOH		Sodium hydroxide
Necrosis		Cell death caused by non-planned cellular injury.
Nematocysts		Specialized stinging cells
NH3		Ammonia
NH4		Ammonium
Nitrate		NO3 the final product in the nitrogen cycle. It is not toxic, but can be dangerous at high levels. Nitrate is created by the oxidation of nitrite by nitrobacter bacteria. In a nano reef, nitrate levels should be kept below 10 ppm.
Nitrate (NO3-)		a form of nitrogen that is the end-product of nitrification which is produced by Nitrobacter spp. Nitrate is also the initial substrate for denitrification. Nitrate is not considered very toxic to aquatic organisms. The nitrate concentration in an aquarium will continue to increase unless steps are taken to remove it from the water. The most common way is through regular water changes. Other methods are to use live plants which utilize nitrate for growth or by installing a denitrifying filter.
Nitrification		The process by which ammonia is changed to nitrite, then nitrate, and finally nitrogen gas. See nitrogen cycle.
Nitrification		the oxidation of ammonia to nitrite, and nitrite to nitrate by bacteria belonging to the family Nitrobacteraceae. The most well-known nitrifying bacteria are Nitrosomonas europaea which oxidize ammonia to nitrite, and Nitrobacter winogradskyi which oxidizes nitrite to nitrate. But there are other members of both groups such as the ammonia oxidizers Nitrosococcus mobilis, Nitrosolobus multiformis and Nitrosococcus oceanus, and the nitrite oxidizers including Nitrobacter hamburgensis, Nitrospira marina and Nitrococcus mobilis. Nitrification is the most important process in an aquarium as it forestalls the build-up of ammonia which would otherwise increase to toxic levels. Nitrification takes 30 to 45 days to become established in a new aquarium during which time ammonia and nitrite may reach toxic levels (called new tank syndrome).
Nitrite		NO2 the second product in the nitrogen cycle. Nitrite is a highly toxic substance that is produced by the oxidation of of ammonia by nitrosomonas bacteria. It is easily removed with biological filtration.
Nitrite (NO2-)		a form of nitrogen that is produced during nitrification and denitrification by bacteria. Generally nitrite is very transient being quickly utilized by bacteria. Nitrite can accumulate to toxic levels during the break-in or cycling of a newly established aquarium.
Nitrobacter		the genus name for aerobic, chemolithoautotrophic bacteria that convert nitrite to nitrate via oxidation. Rod shaped, often pear shaped (0.6-0.8 to 1-2 microns in length).
Nitrogen Cycle		The nitrogen cycle describes how organic wastes break down in the aquarium. Fish wastes naturally decompose into ammonia, which is highly toxic. Nitrosomonas bacteria process the ammonia into nitrite, which is also toxic. Nitrobacter bacteria then break down the nitrite into nitrate, which is much less harmful. This is as far as the cycle goes in most tanks, though under the right conditions, the nitrate is further broken down to free nitrogen gas.
Nitrosomonas		the genus name for aerobic, chemolithoautotrophic bacteria that convert ammonia to nitrite via oxidation. Shaped as short rods to ellipsoidal cells (0.8-1.0 to 1-2 microns in length).
NO		Normal output fluorescent light
NO2		Nitrite
NO3		Nitrate
NSW		Natural seawater
NTD		Neon Tetra Disease
NTS		New Tank Syndrome
O2		Oxygen
ORP		Oxidative redox potential
Oxidation		the process of removing one or more electrons from a compound or ion. When ammonia is oxidized to nitrite, or nitrite then oxidized to nitrate, electrons are removed from the substance being oxidized.
PAR		Photosynthetic Available Radiation. Wavelengths of light that can be absorbed by chlorophyll or other light harvesting pigments.
Parameter		A particular physical, chemical, or biological property that is being measured.
Parasite		An organism that feeds on the tissues of another organism. Parasites are one of the major causes of disease in aquarium fishes.
PAS		Photosynthetic Action Spectrum
Pathogenesis		Origin of a disease
PBT		Powder Blue Tang
PC		Power compact fluorescent light
PF		Power Filter
pH		Provides a measure on a scale from 0 to 14 of the acidity or alkalinity of a solution where 7 is neutral and <7 is acidic and >7 is basic; concentration of hydrogen ions.
PH		Powerhead, water pump
Phenols		a group of low molecular weight organic compounds that are responsible for smells, such as the “fishy smell” sometimes associated with aquariums.
Phosphate		A nutrient that can case uncontrolled growth of algae in the aquarium. It can also toxic in high concentrations and must be kept to a minimum in reef aquariums. Phosphate can be easily removed by a number of commercially available filter medias.
Phosphorus (P)		occurs in water as phosphate (-PO4) in two general forms: ortho- and organic. The orthophosphate form which is utilized by plants and algae for growth is also called soluble reactive phosphate (SRP). The chemical formula is PO43-. This is also the form of phosphorus that test kits can measure.
Photoperiod		The length of time your aquarium lights are turned on.
Plankton		The passively floating or weakly motile aquatic plants (phytoplankton) and animals (zooplankton).
PO4		Phosphate
Polyp		An individual of a solitary coral or one member of a coral colony.
Powerhead		A small submersible pump commonly used inside an aquarium to provide additional water movement. Several powerheads can be used in conjunction with a controller unit to simulate natural wave actions.
PPM		Parts per million, equivalent to mg/l (milligrams per litre)
Protein Skimmer		This mechanical filter, also called a foam fractionator, sends many small bubbles through a column of water to separate dissolved organic compounds from the water. They come in many varieties such as venturi, counter-current, and co-current. They are only effective in salt water. They may be placed in the tank, hung on the side, or placed in a sump.
PS		Protein Skimmer
PUFA n-3		Polyunsaturated Fatty Acid (omega-3 fats)
PUR		Photosynthetically Usable Radiation
Pure Water		water which contains nothing but a few dissociated hydrogen and hydroxyl ions. Pure water contains no salts, gases, bacteria or other such substances.
PVC		Poly vinyl chloride, used for piping / plumbing
PWC		Partial Water Change
QT		See Quarantine Tank
Quarantine Tank		A tank (other then your display) set-up specifically to monitor and prevent outbreaks of problems in your main display aquarium when you bring home new fish, inverts, etc. Usual time in a QT is 2-4 weeks. Most commercial Aquariums (Monterey Bay, Aquarium of the Pacific, etc.) always Quarantine for minimum of 4 weeks.
RBD		Red Band Disease
RCS		Red Cherry Shrimp
Redox Potential (ORP)		measures whether a solution would tend to accept or give electrons. The name, redox, comes from the common terms of reducing (giving electrons) or oxidizing (accepting electrons). A high redox value means the water will accept electrons. Water which is aerobic is an oxidizing environment and thus has a high redox potential. Conversely, anaerobic waters are reducing environments with low redox values.
Reflector		Something having a polished surface for reflecting light. Reflectors are placed around aquarium lights to guide and direct their light downward.
Refugium		An area separate from the display tank (often in a sump), that is meant to be a refuge for organisms like “pods”. Macroalgae is often found in refugiums as both a habitate for the pods and a form of nutrient export (through trimming excess growth). Refugium organisms are either not widespread in the main tank (i.e. the lack of pod predators) or are not desired as display species; although some refugiums achieve a display quality as highlight organisms like sea grasses.
Reverse Osmosis		This is a purification method for tap-water. Prefiltered tap water is pushed through a reverse osmosis membrane. Water that makes it through is considered pure, while water that does not, is sent through a special tube and is rendered impure. As it relies on water which is able to pass through the membrane, it also generates a large quantity of “waste” water which cannot be used. This is one of the best, but slowest methods of tap water purification. Reverse Osmosis units produce purified water at extremely slow rates, sometimes as low as 10 or 15 gallons per day (depending on your water pressure and temperature).
RO		See Reverse Osmosis
RO/DI		Reverse osmosis with deionization. DI filtration alone is highly effective at purification, but the filter media exausts quickly. By adding it to the end of a reverse osmosis filter, near 100 percent purity can be acheived, while extending the life of the DI resin.
RR		Reef Ready
RTAW		Reefing the Australian Way
RTBS		Red Tailed Black Shark
RTN		Rapid Tissue Necrosis
SAE		Siamese Algae Eater
Salinity		A measure of the salt concentration of water.
SC		Soft Coral
SF		Sponge Filter
SG		Specific gravity
SG		See Specific Gravity
Si		Silicon
SiO2		Silicon dioxide
Soft Coral		Common name for species of the anthozoan order Alcyonacea of the subclass Octocorallia. In contrast to the hard or stony corals, most soft corals do not possess a massive external skeleton.
SP		Sump Pumps
Specific Gravity		The ratio of density of a given liquid to that of pure water. Specific gravity is used to measure the salinity of seawater as compared to distilled water. Distilled water has a specific gravity of 1.000 while natural seawater has a specific gravity of about 1.025. SG readings are also effected by temperature.
SPS		Small polyped Scleractinian (stoney) coral
Sr		Strontium
SSB		Shallow Sand Bed
Starphire		PPG’s high clarity glass which comes from minimal iron impurities
STN		Slow Tissue Necrosis
Sump		A container that houses items such as wet/dry filters, skimmers, heaters, and refugiums. Sumps are generally kept below the display aquarium. Water drains into the sump from the aquarium above, and is pumped back to the aquarium.
SW		Saltwater / seawater
Sweeper Tentacle		A coral polyp tentacle that has an increased number of nematocysts and elongates in order to ‘sting’ neighboring corals and sessile invertebrates. A tool in the competition for space and resources.
SWS		Seneye Web Server
Tannins		A low redox reading can be an indication of heavy organic loading. As the level of organic matter increases, there is more heterotrophic bacteria activity which consumes oxygen. This reduces the redox potential. There is no one correct redox number for an aquarium. Redox will change over the course of a day. It will be lower in the dark than in the light because photosynthesis adds oxygen to the water which increases the redox potential.
TB		Tank Breed
TDS		Total Dissolved Solids
TF		Tropical Freshwater
TFC		Thin film composite, type of RO membrane
TFH		Tropical Fish Hobbyist
TR		Tank Raised
Trace Elements		Elements that occur naturally in small quantities in seawater. These are required for survival by many reef organisms, and include calcium, iodine, strontium, molybdenum, lithium, and barium.
TWP		Tap Water Purifier from Aquatic Pharmaceuticals
UGF		Undergravel filter
UV		Ultra violet light
VHO		Very high output fluorescent light
Water Change		The process of removing a certain percentage of water from a reef aquarium and replacing it with newly mixed saltwater. This process helps remove disolved organics, nitrates, detritus, and replenishes trace elements. In a nano reef, 10 percent changes are recommened every week, or 20 percent every other week.
Wet/Dry Filter		A biological filtration system that is exposed to the air to aid nitrification. This system typically consists of a large box that is placed underneath the aquarium. Water passes down into the filter over a filtration medium where bacteria remove toxins. The water is then pumped back up into the tank. A sponge or other mechanical filtration medium may also be used in a wet/dry filter.
Zoanthid		An anemone of the family Zoanthidae, usually found in intertidal areas and coral reefs. Commonly kept in reef aquariums for their wide range of colors and ease of care. In some species the polyps separate from each other almost completely after budding, while in other species, the polyps are all interconnected by a common mat of tissue
Zooxanthellae		A group of dinoflagellates living endosymbiotically in association with one of a variety of invertebrate groups (e.g., corals). In corals, they provide carbohydrates through photosynthesis, which are used as one source of energy for the coral polyps. They also provide coloration for the corals.