Aquarium glossary
A B C D E F G H I J K L M N O P Q R S T U V W Z
A  
Abiotic Nonliving
Acclimatization The process of slowly introducing a new organism such as a fish to a new environment so that it can adapt to environmental factors such as temperature and water condition.
Acid

The opposite of a base. A substance that, if dissolved in water, creates a solution with a pH of less than 7.

Acidic A water condition where the pH lower than 7.0. Acidic water may be a sign of overfeeding.
Acidophile Any organism that prefers acidic conditions with a low pH. Includes fish from the Amazon and forest pools in West Africa.
Acontia The stinging tentacles of sea anemones which are used to paralyze and ward off prey. They push out through the mouth opening and through special pores (cinclides) in the body-wall.
Acquired immunity When an organism develops the ability to prevent a particular infection.
Acropora Commonly known as Staghorn coral, Acropora are branching stony coral which are commonly found on natural reefs. Generally they prefer strong, random current and strong lighting.
Actinic bulbs A type of fluorescent light bulb which produces light at the blue end of the spectrum. Useful for maintaining the photosynthetic process in marine aquariums. Often used to make corals glow fluorescently and to maintain the health of other marine organisms such as marine algae and anemones.
Activated carbon A granular form of carbon which is highly porous. It is used in aquarium filtration to absorb dissolved impurities from fresh or marine water.
Aerobic Describes biological activity that occurs only in the presence of oxygen.
Algae Small aquatic plants typically found in water or wet places, can range in size from single-celled organisms to giant kelp. Their growth is proportional to sunlight and available nutrients and their presence may reduce the levels of dissolved oxygen.
Alkaline The opposite of an acid. A substance that, if dissolved in water, creates a solution with a pH greater than 7.
Ammonia Ammonia (NH3) is excreted by fish and is also generated by rotting fish and plant material. It is the first phase of the nitrogen cycle and is the most toxic to fish of all the nitrogenous chemicals.
Anaerobic Describes biological activity that occurs only in the absence of oxygen.
Anal fin A fin located on the underbody of the fish approaching the tail.
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B  
Bacteria A group of single-cell microorganisms, they may result in infections or disease in animals and humans.
Bubble nest A nest which is created from saliva and tiny air bubbles. Used during incubation to protect and insulate the eggs of fish such as the Siamese Fighter.
Biological filtration Improves water conditions using special filter media combined with bacteria to breakdown harmful compounds such as ammonia and nitrite.
Brackish Water that is a mixture of freshwater and seawater. Occurs naturally in river estuaries and lagoons.
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C  
Calcium Carbonate Calcium carbonate (CAC03) is a compound found in chalk, limestone, shells and the skeletons of invertebrates. It can be used to increase the pH of water.
Carbon A non-metallic element . It is used in aquarium filtration to absorb dissolved impurities from fresh or marine water.
Caudal fin The tail fin of a fish.
Chemical filtration A method of filtration that uses activated carbon or other chemicals to absorb and neutralize harmful substances in water.
Cichlidae Refers to a family freshwater fishes commonly known as cichlids. The family includes as many as two thousand species, many of which are native to India, South America and Africa.
Conductivity The ability of a solution to carry an electric current. Measuring conductivity can determine the overall mineral content of a water sample.
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D  
Decapod Having ten feet. Examples are crustaceans including shrimps, lobsters and crayfish.
Denitrator A piece of biological filtration equipment which removes nitrate (NO3) from water. A denitrator encourages the growth of anaerobic bacteria which convert the nitrate (NO3) into nitrogen gas (NO2), the gas can then escape into the atmosphere.
Detritus Organic material resulting from decomposing plants or animals.
Dorsal fin An upward projecting fin on the back of a fish. It provides stability and assists with swift change of direction.
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E  
Echinoderm A type of invertebrate that exhibit 5-part radial symmetry and a hard outer shell. Examples include starfish, sea urchins, and sea cucumbers.
Eyestalk A small, sometimes moveable, appendage which supports the eye of certain crustaceans such as crabs and shrimp.
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F  
Filter feeder An animal that obtains its food by straining tiny particles from water. Examples include oysters and clams.
Fingerling A young fish, generally in its first year of life, which is between the fry and adulthood stages of fish development. In larger species the fish may be about the size of a finger.
Foam fractionation The removal of proteins and organic material from water using a foaming action. Protein skimmers use this method.
Foot A muscular appendage found at the base of many mollusks to maintain contact with a surface or assist with travel.
Freshwater Water that does not contain significant amounts of dissolved solids of any type. It is generally found in inland lakes, rivers, creeks and the like.
Fry A newly hatched or born fish.
Fungi A group of organisms which are often microscopic and do not contain any photosynthetic pigment, they act as decomposers or parasites. Parasitic fungi can infect plants and animals.
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G  
Gastropod A type of mollusk which includes snails and slugs. Characteristics include a single coiled shell or no shell at all and a large muscular foot which is used for movement.
GH Also referred to as general hardness, this is a measurement of the calcium, magnesium and other ions present in water. General hardness is measured in either German degrees of hardness (dH) or parts per million (ppm) and can be used to determine if water is ‘soft’ or ‘hard’.
Gill A respiratory organ used by fish which obtains oxygen from water and releases carbon dioxide.
Gill arch The bone or cartilage in fish which support their gills.
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H  
Hardness A term used to describe freshwater which refers to the concentration of dissolved minerals in the water.
Herbivore An animal that eats only plants.
Host An animal or plant that harbors a parasite or disease. The parasite uses the host to gain nourishment and support and may kill or weaken the host.
Hydrometer An instrument used to measure the salinity of water.
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I  
Immunity The ability of an organism to resist infectious disease.
Impeller Rotating part of a pump or filter which propels the water through the device.
Invertebrate An animal that does not have a backbone such as a crayfish.
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J  
Jaubert Plenum A biological filtration system for marine setups which uses a protein skimmer, deep sand bed, and an air cavity (plenum).
Juvenile A young fish that has not reached sexual maturity.
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K  
Kalkwasser Purified fresh water mixed with calcium hydroxide. When dissolved, it is used as an additive to introduce inorganic calcium to marine tanks. Also known as limewater.
KH Refers to carbonate hardness which measures the amount of dissolved carbonate and bi-carbonate ions in water. It is used to measure the buffering capacity of water i.e. the ability of water to resist a change in PH. Water with a low KH is subject to rapid shifts in PH which can stress fish and lower their immunity.
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L  
Labyrinth fish A fish from the Anabantoidei family. Characterized by a respiratory organ which allows them to obtain oxygen from the air and enables them to live in poorly oxygenated water. Examples incude Siamese Fighters and Gouramis.
Live Rock Rock that still has marine organisms such as worms, small crustaceans, polyps, algae, sponges and urchins on it. It is used in saltwater aquariums to initiate and continue the nitrogen cycle.
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M  
Macroalgae Refers to the varieties of algae that can be seen by the human eye such as seaweed. The opposite of microalgae.
Marine Describes a saltwater environment or anything associated with the sea or ocean.
Mechanical filtration A method of filtration which removes particles from water by passing it through filter media such as polyester or foam.
Microalgae Refers to the small varieties of algae that cannot be seen by the human eye. Microalgae can be observed using a microscope. The opposite of macroalgae.
Mollusks An invertebrate animal characterized by a soft body that is enclosed by a hard outer shell. Examples include clams, snails, and scallops.
Mysis A small crustacean commonly used as food for marine fish.
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N  
Nitrate Nitrate (NO3) is a form of nitrogen and is the final product of the nitrogen cycle. It can be harmful to fish, especially marine invertebrates, if it builds up to a high level. Partial water changes can reduce the level of nitrate in aquarium water.
Nitrification A process which employs bacteria to maintain the nitrogen cycle converting the ammonia excreted by fish into nitrite and then into the less harmful form, nitrate.
Nitrite Nitrite (NO2) is a form of nitrogen and is the product of the first phase of the nitrogen cycle. Nitrite at low levels can be harmful to fish.
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O  
Omnivore An organism that uses both plant and animals as food sources.
Osmosis The process by which a fluid passes through a semi-permeable membrane in an attempt to equalize the concentration of dissolved solids on either side of the membrane.
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P  
Parasite A parasite is an organism that lives in or on another host organism and gains shelter and nourishment at the expense of the host.
Pelvic fins A pair of fins of varied size which are located on the underside of the fish between the pectoral fins and the anal fins.
PH A scientific measurement of the amount of hydrogen and hydroxyl ions dissolved in water which determines the acidity or alkalinity of a solution. Using a scale ranging from 0 to 14 a PH of 7 represents a neutral solution, values less than 7 indicate acidity and values greater than 7 indicate alkalinity.
Photosynthesis The process by which green chlorophyll-containing plants utilize sunlight, water and carbon dioxide to produce oxygen and carbohydrates.
Popeye A condition where one or both eyes of a fish protrude and appear to be ‘popping out’. Can be a sign of disease and if left untreated may result in eye loss.
Powerhead A submersible water pump used to provide water circulation or to power undergravel filters.
ppm An abbreviation for parts per million. It is a unit of measurement used when describing the concentration of a mixture and is comparable to milligrams per litre (mg/l).
Protein A complex molecule made up of amino acids. Protein is important in the diet of fish but the metabolism of protein by fish also results in nitrogenous waste such as ammonia.
Protein skimmer A device used in saltwater aquariums to remove organic impurities from the water by creating a proteinous waste rich foam which builds up in a small collector and can be periodically discarded. The device can also be referred to as a foam fractionator.
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Q  
Quarantine The isolation of a fish for a specified period of time to assess whether or not the fish is free of disease. It should be undertaken before introducing a new fish to a larger group in order to minimize the spread of any disease.
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R  
Reef aquarium A saltwater aquarium containing live corals, fish and other invertebrates. Particular attention is paid to lighting and water conditions in order to simulate a natural reef.
Respiration The metabolic process in which an organism takes in oxygen and then releases carbon dioxide and water into its environment.
Reverse osmosis A water purification method used to remove salts, metals, and minerals. The process is highly effective but produces a large amount of waste water. This process is also referred to as RO.
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S  
Salinity A measure of the dissolved salts in water. Can be measured by specific gravity.
Salt creep The gradual buildup of salt deposits on the side of marine aquariums as a result of evaporation.
School A group of fish, usually from the same species or sub-species, that swim together in order to trap prey or protect themselves from predators.
Shoal A group of fish, from different species, that swim together in order to order to trap prey or protect themselves from predators.
Specific gravity A measurement used to describe the salinity of water. It is the ratio of the density of a particular solution to the density of pure water.
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T  
Thermostat An instrument that automatically controls a heating or cooling device in response to temperature change in the environment. Thermostats are typically found in devices such as aquarium heaters and chillers.
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U  
Ultraviolet Refers to the invisible rays of the light spectrum which are beyond violet light. This type of light can be used in aquariums to kill harmful bacteria and control disease. It is often abbreviated to UV.
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V  
Ventral fins Another name for the pelvic fins. A pair of fins of varied size which are located on the underside of the fish between the pectoral fins and the anal fins.
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W  
Water change To remove a portion of the water from an aquarium and replace it with clean un-polluted water. This helps to reduce the build-up of waste and replenishes certain minerals and trace elements which are depleted over time.
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Z  
Zoea An early larval stage in the development of decapod crustaceans such as crabs and shrimp.
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