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Abramites	omnivorous South American charcins: commonly known as "headstanders" because of the posture they assume while swimming
Acanthophthalmus	an out-of-date name, often seen in the aquarium literature, for Southeast Asian loaches, Family Cobitidae
Acanthurus	type genus of Family Acanthuridae, commonly known as tangs or surgeonfish, herbivorous grazers often found around coral reefs
Acara	a name often used in the older aquarium literature for several species of large South American cichlids now assigned to several genera; some species known in the aquarium trade remain undescribed
Acclimation	the process of slowly introducing a fish or other organism to new water conditions, usually following transport form one aquarium to the other
Acetabularia	a green tropical marine alga commonly known as "mermaid's wineglass" that grows in upright colonies on hard substrates
Acid	a chemical compound that dissociates in solution to yield one or more hydrogen ions and a negatively charged ion; a solution with a pH less than 7.0
Acipenser	Sturgeons, primitive bony fish found in both freshwater and marine habitats
Acontia	Filaments extruded from pores at the base of the pedal disc of certain sea anemones, thought to be utilized for defensive purposes
Acorus	Sweet flag, flowering marsh plants of the Family Arum with tough, strap like, emergent leaves that have a pleasant smell when crushed; a cultivar with variegated leaves is often grown in garden ponds.
Acropora	a large genus of branching corals that are typically found in brightly lit waters with high oxygen concentration and heavy turbulence; several species are popular with aquarists owing to the ease with which they can be propagated.
Acroporid	Any coral in the Family Acroporidae
Acrorhagi	Inflated sacs that protrude from beneath the tentacles of certain anemones, bearing stinging cells that prevent other anemones from growing too closely
Actinic	artificial lighting that is rich in blue wavelengths, used in aquariums to mimic light conditions several meters below the surface
Actinopharynx	the body opening of cnidarians that serves as both mouth and anus
Actinopyga	sea cucumbers found in shallow waters in the tropical Atlantic and Caribbean, popular with aquarist because of the habit of burrowing into the substrate
Activated Carbon	a filtering medium prepared by exposing organic materials such as bones or coconut shells to high temperatures and steam; this highly porous material absorbs dissolved organic compounds and large ions, such as iodide, from aquarium water
Adamsia	sea anemones often found living on the mollusk shell occupied by a hermit crab
Adductor muscle	in bivalve mollusks, this muscle holds the two halves of the shell together when contracted
Adenosine triphosphate	abbreviated as "ATP" a molecule employed by all living cells for transferring energy derived from food metabolism into cellular chemical reaction
Adinia	an omnivorous killifish found in brackish waters of the southern United States; suitable for a temperate aquarium
Adipose fin	a small fin, composed of fatty tissue, located between the dorsal and caudal fins of some fish, notably charcins and catfish
Aequidens	Flag cichlids, South and Central American species with territorial behavior and undemanding appetite
Aged water	1) tap water that has been left to stand, and from which chlorine has been neutralized; 2) water from a healthy, well-established aquarium that does not contain large amounts of nutrients
Ahermatypic	reffering to corals that lack zooxanthellae
Aiptasia	small sea anemones that often multiply to plague proportions in maring aquariums with bright light, heavy loads of organic matter, and excessive nutrients in the water
Air pump	a device for delivering air under low pressure to aquarium equiptment connectrd to it by means of flexible tubing; older models employ a reciprocation piston, while most modern versions use a bellows operated by a electric vibrator to achieve pressurization
Airlift	a device that utilizes the principle of displacement for pumping water; forcing air in near the bottom of a tube immersed in the aquarium causes water to be pushed out the top of the tube as the column of air rises.
Airstone	any of several types of porous diffusers used to release tiny air bubbles into the aquarium; made of fused glass spheres, plastics, or even limewood
Air stripping	a synonym for protin skimming
Alcyonacean	a soft coral lacking an axial skeleton
Alcyonium	a typical soft coral without an axial skeleton, popular with aquarists
Alestes	omnivorous African characins, such as the nurse tetra
Algae	any of a wide variety of photosynthetic organisms lacking a vascular system; may be unicellular, filamentous, or, in the case of seaweeds, large and complex in form
Algae-eater	any species of fish or invertebrate that feeds on encrusting and filamentous algae: introduced into the aquarium primarily for control of such growths
Algae turf scrubber	aquarium water purification system designed at the Smithsonian Institution and employing various species of algae growing on plastic mats in specially designed tanks to remove pollutants from the water
Alkalinity	a measure of the ability of a solution to neutralize acid without a change in pH, expressed in milliequivalents per liter
Allelochemicals	substances released into the water by one species that inhibit the growth of one or more potentially competing species, characteristic of some cnidarians kept in minireef aquariums
Allopatric	literally "different country," referring to the occurence of sister species that are geographically seperated although sharing a common ancestor.
Alpheid	a member of the snapping shrimp family, marine crustaceans with one appendage modified for the production of a sudden popping sound that is thought to deter predators; some members have the sound appendage modified for digging, have lost the ability to pop, and rely on partnership with certain fish for protection
Alpheus	snapping shrimps, including A. armatus, found in association with the anemone Bartholomea annulata in the tropical Atlantic
Alternanthera	a freshwater flowering plant of the amaranth family of South America used in aquariums for its upright habit and rapid growth
Alveopora	stony corals, Family Poritidae, generally considered difficult to maintain in the aquarium
Amblycirrhites	hawkfish, Family Cirrhitidae, found in both the Atlantic and Pacific regions
Amblygobius	Indo-Pacific gobies, Family Gobiidae, that typically shelter in the burrow abandoned by another animal, although the most popular aquarium species, A. rainfordi, is found near coral heads
Amines	chemical compounds containing the amino radical (-NH2+) amino acids are the chemical units from which protines are constructed
Ammannia	a fast-growing flowering aquatic plant of the loosestrife family from tropical Africa
Ammonium	the ionized form of ammonia (NH4+)
Amoebocytes	specialized cells in the body of a sponge that are involved in food transport withen the animal
Amphipod	small, laterally compressed freshwater or marine crustaceans that often are transported into aquariums unintentionally; they are harmless scavengers and are eaten by many types of fish
Amphiprion	one of two genera of pomacentrid fish that associate with sea anemones; also called clownfish, they are popular with marine aquarium hobbyists
Amplexidiscus	a single species of corallimorph, commonly reffered to as the "giant mushroom polyp," capable of feeding upon small fish that become trapped in its stubby tentacles
Ampulla	part of the water vascular system of echinoderms; like the bulb of a medicine dropper, it forces water into, or draws water from, an individusl tube foot
Amyloodinium	a parasitic dinoflagellate that infests the gills and epidermis of many species of marine fish, often fatally; synonyms are "marine velvet"and "coral fish disease"
Anabantid	referring to any of the labyrinth fish Family Anabantidae, freshwater species characterized by an organ that permits them to breath atmospheric oxygen
Anableps	type of genus of the "four-eyed fish" family; the unique structure of the eyes of these freshwater fish permith them to see above and below the surface simultaneously
Anaerobes	bacteria that do not require oxygen to carry out metabolism; "facultative anaerobes" can survive in the presence of oxygen, while free oxygen is poisonus to "obligate anaerobes"
Anal fin	the unparied fin arising on the midline of the ventral surface of a fish, anterior to the tail and usually just posterior to the anus and urogenital openings
Anampses	small tropical wrasses, Family Labridae, that feed on benthic invertebrates and are generally difficult to maintain in aquariums
Ancistrus	one of several genera of south American suckermouth catfish, often called 'bristle-nosed plecostomus"
Anemone	a noncolonial anthozoan with tentacles in multiples of six, lacking a calcified skeletal structure and usually attached to a solid substrate by means of the pedal disc
Anemonefish	any of the pomacentrid fish of the genera Amphiprion or Premnas that associate with sea anemones
Angelfish	in freshwater, Pterophyllum, South American cichlids that have long been popular with hobbyists; one species, P. scalare, exists in many cultivated varieties; a marine angelfish is any member of Family Pomacanthidae, all colorful, including small species of Centropyge that generally adapt well to aquarium care, and larger species of Pomacanathus and others that can be challenging to maintain in the aquarium
Anglerfish	predatory fish in the Family Antennaridae that entice prey within striking distance by means of a "fishing pole" formed from the first dorsal fin spine
Angiosperm	any flowering plant, referring to the enclosure of the seed withen a fruit
Aniculus	demon hermit crabs, such as the Indo-Pacific A. strigatus, adapted to utilize empty mollusk shells whose narrow openings render them unusable by other hermit crabs
Anions	ions bearing a negative electrical charge, such as chloride (Cl-)
Annelid	any member of the animal phylum Annelida, the segmented worms
Anomalops	flash light fish, an Indo-Pacific species that occurs in two forms depending upon water depth; bioluminescent due to bacteria living withen a light organ underneath each eye
Anostomus	omnivorous South American Characins; some are known as "headstanders"
Anoxic	lacking free oxygen
Antenna	the elongated sensory appendage of a crustacean
Antennarius	type genus of anglerfish, Family Antennaride, maarine species that lure prey within striking distance by means of a "fishing pole" formed from the first dorsal fin spine
Anterior	referring to the head end of the body of a bilaterally symmetrical animal
Anthelia	colonial soft corals with feathery tentacles; popular with marine aquarists
Anthias	small, colorful sea basses, Family Serranidae, that form large schools and feed on plankton in open waters, suitable for large aquarium displays
Anthopleura	sea anemones, often tinted green by the presence of symbiotic algae; found off the Pacific coast of North America and elsewhere in the Pacific
Anthozoan	litterally "flower animal"; any member of Phylum Cnidaria, Class Anthozoa, characterized by the predominance of the flowerlike polyp form in the life cycle
Antibiotic	a medication that kills or otherwise halts the reproduction of bacteria
Antifoulant	a chemical agent added to paint to prevent encrustation by aquatic organisims such as algae or barnacles
Antiheminthic	any medication used in the treatment of parasitic infestations by worms
Anti-inflammatory	a medication that reduces inflammation, the process by which injured or infected tissues become reddened due to localized expansion of the blood capillaries
Antioxidant	a chemical agent that prevents foodstuffs or other perishables from being degraded through exposure to atmospheric oxygen
Antiviral	a medication that interferes with replication of a virus, a submicroscopic pathogen that must parasitize a living cell for its own reproduction
Anubias	semi-aquatic plants in the aroid family,. native to Africa; sometimes planted in freshwater aquariums
Anus	the opening at the posterior end of the gastrointestinal tract through which feces ar eliminated
Aphanius	egg-laying toothed carps of Europe and Asia; kept by specialist aquarium hobbyists
Aphyosemion	killfish, or egg-laying toothed carps, Family Cyprinodontidae< of Africa< popular with freshwater aquarium enthusiasts
Apistogramma	dwarf cichlids native to Central and South America that are popular with some aquarium hobbyists because of their small size and relatively nonaggressive nature
Aplochellus	sometimes known as "panchax" egg-layingtoothed carps found on the Indian subcontinent
Aplysia	opisthobranch mollusks commonly called "sea hears"
Aplysiid	any member of the mollusk Family Aplysiidae, or "sea hears," characterized by a reduced internal shell; all are vegetarian grazers
Apogon	cardinalfish, Family Apogonidae; schooling tropical marine fish, largely nocturnal; popular aquarium species found near coral reefs
Apolemichthys	reef-dwelling marine angelfish that feed on sessile inverterbrates, making them difficult as aquarium subjects
Aponogeton	freshwater plants, occuring largely in Asia, that grow from an underground tuber; unlike most other aquarium plants they require a period of dormancy with cool temperatures in order to grow properly
Aquaculture	production of aquatic organisms for food, aquarium, orscientific purposes, generally as a commercial venture
Aquaculturist	one who practices aquaculture
Aquarist	one who designs or maintains an aquairum
Aquarium	1) a tank, often fitted with life-support equipment, specifically constructed for housing living aquatic organisms for exhibition, aquaculture, or scientific study, of dimensions appropriate to enclosure withen a building; 2) an exhibit of living organisms in one or several separate containers, intended to give the impression of a window into an aquatic habitat
Aquascape	the physical design of the interior of an aquarium, including rocks or other objects selected and placed in such a way as to cnvey to the viewer the aquarist's impression of an underwater scene
Aquatic	of or living in water
Arachnanthus	one of several genera of tube-dwelling cnidarans that resemble anemones
Aragonite	a form of calcium carbonate deposited as skeletal elements in marine invertebrates such as corals
Arborescent	"treelike," usually in reference to the body structure of certain colonial marine invertebrates such as gorgonian soft corals that branch and rebranch
Arm	among aquarium organisms this trem is properly applied only to the appendages of brittlestars or to the body divisions of sea stars
Artemia	the genus to which brine shrimp, a popular food for both marine and freshwater aquariums, are assigned
Arthropod	any member of Phylum Arthropoda, invertebrates characterized by jointed appendages and an external skeleton composed of chiton, including the terrestrial insects as well as a variety of marine and freshwater organisms
Asexual reproduction	production of offspring without the union of gametes; examples include budding in some cnidarians, regeneration of separated cells of sponges, and rooting cuttings of many types of flowering aquatic plants
Aspidontus	Indo-Pacific blennies noted for their mimicry of cleaner wrasses, allowing them to get close enough to other fish to bite them
Assimilate	In biology, the incorporation of nuterent molecules into the body structure of the consumer
Astraea	tropical marine gastropods often collected from florida for algae control in the aquarium
Astrangia	star corals, stony corals usually forming small colonies and encrusting rocks; so named for the appearandce of the skeletal cups from which the polyps protrude
Astronotus	the oscar, A ocellatus, arguably the most popular member of the cichlid family, growing to almost a foot (30 cm) in length and becoming quite tame
Astropecten	an Indio-Pacific sea star with large, distinctive spines at the edges of the arms; it feeds at night on small bivalve mollusks
Astrophyton	the Carribbean basket star, a large echinoderm with multigranched arms that are used for capturing plankton; often imported but does poorly in the aquarium
Astyanax	characins of Mexico, Central, and South America, notably the blind cave tetra, A. Fasciatas mexicanus
Aulonocara	peacock cichlids endemic to Lake Malawi, Africa
Aurelia	the common moon jellyu, a sea jelly found worldwide and often exhibited in public aquarium
Avrainvillea	green tropical seaweeds that grow upright from a base imbedded in the substrate; they have a characteristic texture resembling felt
Axial skeleton	the stiffened, protenaceous internal structure that provides rigidity to the bodies of gorgonians
Azolla	mosquito ferns, tiny floating plants commonly grown in both freshwater aquariums and garden ponds

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