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Freshwater Fish and Resources

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The process by which a filter media traps unwanted molecules.


The process of slowly introducing a fish to new water conditions .


solution (i.e. water) with a pH less than 7.0 .


Water with a pH of less than 7.


A plastic material used to construct fish tanks, filters and accessories.

Activated carbon

A commonly used chemical filter media.

A highly porous filtering medium prepared by exposing organic materials such as bones to high temperatures and steam; absorbs dissolved organic compounds and large ions such iodide from water.

Adipose Fin

A small fin located behind the dorsal fin and in front of the caudal fin. 

A small fin composed of fatty tissue located between the dorsal and caudal fins of some fish such as characins and some catfish .


A term used to describe an organism that needs oxygen to survive.

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.

Air Pump

A device for delivering air under low pressure to tank equipment via tubing.   


A device that attaches to the air pump to create various bubble effects.

A porous diffuser used to release tiny bubbles; usually made of fused sand.


Any of a wide variety of photosynthetic organisms lacking a vascular system; maybe be unicellular, filamentous, or complex (seaweeds).

Algae Eater

A fish or invertebrate which feeds on algae. Example: Siamese Flying Fox, Otocinclus affinis.

Alimentary canal

The tube of the digestive system through which food passes, where digestion takes place.


Water with a pH between 7 and 14. Also known as Basic.


A measure of the ability of a solution to neutralize acid without a change in pH.

Ammonia (NH3)

A dissolved gas that even in low concentrations is toxic to fish. It is produced by the breakdown of organic waste products.

A colourless, toxic gas with a strong odour; NH3.


The ionized form of ammonia; its properties are similar to those of alkali metals sodium and potassium; NH4.


A labyrinth fish; they have an organ that permits them to breathe atmospheric oxygen.

Anal fin

Single fin mounted vertically below the fish.

The unpaired fin in the mid line of the ventral surface of a fish, anterior to the tail and usually just posterior to the anus.


A term used to describe an organism that lives in an environment with little or no oxygen.


A condition lacking free oxygen.


Referring to the head end of the body of a bilaterally symmetrical animal.


A medication that kills or otherwise halts the reproduction of bacteria.

Anti oxidant

A chemical agent that prevents food or other perishables from being degraded through exposure to atmospheric oxygen.


One who designs or maintains an aquarium.


Brine shrimp. 
The genus to which brine shrimp belongs.




A transformer which changes the voltage from your house outlet to the voltage needed to power different types of lighting.


Whisker-like growths around the mouth, used for finding food and communication; a sensory organ.


Compounds that make water Alkaline. If water contains more acids than basses it's acidic. If it has more basses than acids it's alkaline.


A filter media used for the colonization of bacteria.

Bio load

The demand placed upon the life-support system as a result of the metabolism of all the organisms present in the tank.


A nutrient need for fatty acid synthesis in plants and animals.


The Natural environment of a organism.


A rotating pleated structure over which a stream of water is directed as part of a biological filtration system where nitrifying bacteria grow.

Black Water

Water that has a dark cola-like color caused by Humic acids, it has a very low pH and is very soft, often associated with the Amazon River basin.


The aquatic larva of a gnat, red in colour, sold as frozen fish food.

Box filte

A device usually placed inside a tank, using an airlift to draw water through polyester fiber and other media inside it.


A combination of fresh and sea water, as occurs naturally in estuaries. Salinity: 15 - 20 ppt, pH 8.0

Breeding tank

An aquarium set up for the breeding of fish.

Brine shrimp

Artemia salina and its close relatives, crustaceans often fed to fish.

Bubble nest

A term used for a nest which is constructed of tiny air bubbles, produced by the male fish. It is used to protect the the eggs and fry. Members of the family Anabantidae are the most widely known users of such nests


A substance added to the water to help maintain the pH. value.

A solution of chemical compounds and water that resists a change in pH when either acid or alkali is added.




Having calcium carbonate incorporated into a body structure, such as skeletal elements or a shell. 


A necessary element used by salt water corals and other organisms for their calcium carbonate skeleton or shell.

Calcium Carbonate

CaCO3, a crystalline solid, insoluble in water, incorporated into supported or protective structures in many animal and plant species.

Canister filter

An aquarium filter with the media enclosed in a plastic can outside the tank, with water leaving and entering the can through hoses leading to and from the aquarium.


Salts of carbonic acid (H2CO3).  In these salts the two hydrogen atoms of carbonic acid are replaced by atoms of a metal.

Carbonate Hardness

The part of the total hardness that is formed by the ions of carbonates(Co3) and hydrogen carbonate(HCo3). It is symbolized by dCH. It is important to know the dCH of your water, as it affects both the ph. and Carbon Dioxide amounts in your water. It is also commonly called "buffering capability". a dCH of 4 to 8 is fine for most fish.

Carbon dioxide(Co2)

Important plant nutrient. The higher the dCH the lower the (Co2). For most aquarium plants a level of 4-6 dCH is ideal.

A colourless, odourless gas (CO2), formed along with water during food metabolism by most living organisms; toxic to fish, it is absorbed by plants during photosynthesis and eliminated by aeration and buffering.


That which feeds principally on animals.


One of several yellow coloured organic molecules important in pigment development and cellular metabolism, such as vitamin A.


Species of several families with elongated sensory barbells, a scaleless skin (sometimes with bony plates), usually bottom-dwelling.

Caudal fin

Single fin at the back of a fish-the tail fin.

fish's tail fin used for locomotion.

Caudal peduncle

The fleshy posterior portion of a fish's body to which the caudal fin is attached.


Any fish in the family Characidae, some known as tetras.

Chemical attractants

Compounds released into the water that stimulate another organism or cell to move toward the releasing organism or cell; females may release an attractant for sperm cells of the same species.

Chemical filtration

The removal of dissolved compounds from water by foam fractionation or absorption on various media.


A gaseous chemical element used in bleaching, water purification, etc., usually added by water suppliers to your water. Toxic levels to fish are 0.2 - 0.3 mg/litre.


A chemical by-product caused when water suppliers combine chlorine with nitrogenous compounds, such as ammonia, which is much more stable than chlorine.


A chemical compound used in water clarifiers. It causes fine particles to stick together to be more easily removed by the filter.


Organisms whose body temperature is the same as that of their surroundings.


Different species of fish kept in the same aquarium.    

Crushed coral

A Calcareous substrate material with pH buffering abilities, for marine aquaria.


Member of the phylum Arthropoda, invertebrate animals with a tough external skin. These include crayfish, shrimps and water fleas such as Daphnia and Cyclops. Copepods(ex. Anchor worm) and brachiurans (ex. Fish louse) are 2 groups of crustaceans that cause fish diseases.


Photosynthetic prokaryotes called "blue green algae".


Establishing a population of beneficial nitrifying bacteria in an aquarium's biological filtration system.


A genus of copepod with a single eye in the middle of the forehead (a tiny crab with claws); harmful to fry; avoid feeding to guppies.




Common water flea, often cultivated as food for fish.


Breakdown of nitrates by anaerobic bacteria into other forms.

The p
rocess in which anaerobic bacteria convert nitrate ions into nitrogen gas.


A loss of colouration; bleaching.


The term used in judging referring to how the show guppy displays itself and swims about.


Organic waste matter that collects on the bottom of fish tanks.

Tiny fragments of decomposing plant/animal matter.

Diatom filter

A device that clears fine particulate matter from water, using diatomaceous earth as media.

Diatomaceous earth

A filter media made up of skeletons of Diatoms, used in Diatom filters, able to filter particles down to microns in size. 


Abbreviation for Degrees of Carbonate Hardness.


A limestone gravel with a small pH buffering ability. 

Dorsal fin

Single fin mounted on top of the fish. Some species have two, one behind the other.

The appendage or fin on the mid back of all fish.


Wingless or stump-winged fruit flies cultured as live fish food




Parasite attached to the out body surface of the fish.


A non-metallic conductor of electricity in which the current is carried by the movement of ions; may be salts, bases or acids.


A water resistant socket for fluorescent lamps. 


A parasite that lives in the body.


Proteins that catalyze chemical reactions in living cells.

Epsom salt

Magnesium sulfate (MgSO4).


An antibiotic; toxic to nitrifying bacteria.


An ecosystem formed where a river meets the ocean. It has fluctuations in salinity due to tidal movement. A natural home of guppies.


Mercy killing to prevent a prolonged and painful death.


Solid wastes; feces.




A term used in the classification of organisms. A family is made up of related Genera.

Filter feeder

A small animal that feeds off tiny food suspended in the water.


Method of cleaning aquarium water, there are 3 basic types. "Mechanical" removes particulate material. Chemical" removal of dissolved substances by passing through a type of media, like carbon. "Biological" which is the process of changing from a harmful substance to a less harmful one, by bacteria. 


Fish behaviour shown by rapid, glancing contact with an object in an effort to displace an external parasite or irritation. "Flashing" refers to the fact that the lighter underbelly is seen momentarily.


A member of Phylum Platyhelminthes. Includes non-parasitic Planaria, as well as parasitic forms.


Asolution of formaldehyde gas in water, used as a preservative in taxidermy, and as therapy in ectoparasite infestations.


Fully formed baby fish.

ecently born or hatched fish.


Nonphotosynthetic eukaryotes that feed via extracellular digestion, sometimes pathogenic.



Gene pool

The total amount of genetic diversity within a species.

General or Total hardness

he sum of carbonate hardness and non-carbonate hardness. Usually expressed in degrees of dH.

Abbreviation for "general hardness: or the total amount of dissolved salts of calcium and magnesium present water.

Physical structure that causes gas exchange across the walls of capillaries between the bloodstream and the water. Other parts include the gill cover, gill filaments, gill raker.

Gill cover

A hard bony plate covering the gills.

Gravid spot

A darker but transparent area under the base of the penduncle which female guppies possess; visible in very young female fry.



Hard water

Water with a high concentration of dissolved salts.

Such water than contains dissolved salts of calcium and magnesium in a concentration greater than 200 ppm.


Small live bearing fish from the coastal southeaster U.S., including the least killifish, H. Formosa, the smallest North American vertebrate.


Uniformity; in fishes it refers to a lack of variation among a group, for instance the fry from a strain of guppies.


The offspring resulting from crossbreeding between two different species; in guppies, the resulting fish from a cross between two different strains.


A freshwater hydrozoan resembling a tiny sea anemone, an aquarium pest that is sometimes a problem in breeding because it preys on fry.

Hydrogen peroxide (H2O2)

Sometimes added to tank water to increase the oxygen content as it dissociates rapidly into water and free oxygen; also used as a disinfectant for treating fish wounds.


A device used for measuring specific gravity usually as a measure of the salinity of water. 




A very common parasitic disease characterized by white salt-like specks all over the fish.

An infestation of the skin of a freshwater fish by the protozoan parasite Ichthyophthirius multifillis.



The study of biological science concerning morphology, physiology and taxonomy and ecology of fish.


An abbreviation for inside diameter, used when measuring tubing dimensions.


Microscopic organisms, often ciliated protests and rotifers cultured as a food for fish fry.


An animal with no backbone. 


A chemical element present in seawater and essential for certain marine organisms; also found in table salt (note: it is not toxic).


Positively or negatively charged particles.





K or Kelvin

A temperature reading used to rate the color of lite bulbs. 5500 degrees K is equal to sunlight.


"German hardness", a scale to measue alkalinity or carbonate hardness.


Any euphausid crustacean (Euphausia superba) from the sea, sold frozen or freeze-dried as fish food.



Lateral line

A line of sensory scales along the sides of fish that enables them to detect vibrations and electrical impulses from other fish. 

ies usually along the middle of each side of a fish; senses changes in water pressure so the fish can control its swimming.


Fish which bear live young which have already hatched from egg form inside the fish.


Curvature of the spine induced by malnutrition in fish.


A measurement of light intensity. (1 lumen=10.76 lux). 




Complex celled algae found in marine aquaria i.e.: Calurpa.


Common name for rock dwelling African Cichlids from lake Malawi.

Mechanical filtration

Water purification whereby particulate matter passes over medium (floss, foam) to remove it from the tank.


The process of deriving energy from food molecules by a living thing.

Metal Halide

A very intense type of lighting used in marine and freshwater plant aquaria.

Methylene blue

A chemical dye used as an aquarium medication or disinfectant (useless as the latter); toxic to nitrifying bacteria.


Single celled algae often growing in strands called hair algae.


A unit of electrical conductance: how easily electricity flows through a material.


The exudates of a male fish containing his sperm.


Fish wastes and other solid matter accumulated in the tank, partially decomposed, which needs removal.




The first larval stage of the brine shrimp.


A roundworm; some are parasites an some are fed to fish.


Mildly toxic end product of biological filtration. Can be used as a gauge to tell when a partial water change is needed.


Middle element of the biological cycle.

The end product of ammonia after being converted by bacteria.


Any bacteria capable of oxidizing ammonia.


A bacteria that was thought responsible for changing nitrite to nitrate (research disproves this; other bacteria are probably involved).

Nitrogen cycle

The formal name for the biological cycle in which toxins are broken down into less harmful products by Aerobic bacteria. 


A bacteria that was thought responsible for changing ammonia to nitritre (research disproves this; other bacteria are probably involved).




An abbreviation for outside diameter, used when measuring tubing dimensions.


An organism that eats both plant and animal matter (ie. the guppy).


Known as velvet disease, similar to ich but more deadly.

A microsopic dinoflagellate parasite of freshwater fish, which causes "velvet".


Control of the water and electrolyte balance in the body.

Osmotic pressure

The movement of water across a semipermeable membrane due to the difference between solute concentrations on both sides.


The escape of free gasses (ie. Carbon dioxide or oxygen) from the surface of the water.


A gas used in aquarium systems to break down organic waste, raising redox levels.


Feproduction whereby fertilized eggs are incubated within the parent's body and are released hatched (ie. guppy).




An organism living on or within a host, usually causing harm.


Produces bacterial disease.

Pectoral fins

Paired fins, one on each side of the body located behind the gill covers.


The flesh area to which the the caudal fin is attached.


Measurement of the degree of water acidity. It is determined by the amount of acids and bases in the water. If the amounts are equal it is called neutral with a number rating of 7.0. If more acids it is called acidic with number rating of less than 7.0, if more base it is called alkaline with a number rating of more than 7.0.


An element introduced into the aquarium through organic or inorganic means that promotes excessive algae growth. Can be removed through water changes. 


The characteristics shown in an individual of the genetic traits it inherited; also that which is shown as a result of environment and genes.

Piperazine citrate

An anthelmintic which is used to treat intestinal worms (Camallanus).


Free-swimming flat worms, aquarium pests which may prey on fry and compete for food


Microscopic organisms, both plant and animal which is an important food source.


The family to which the guppy and molly belong.

Power filter

water filter which is powered by an attached motor.

Power head

An electric pump that connects to the under gravel filter tubes to greatly increase the water flow.


Parts per billion, equal to micrograms per litre.


Parts per million, equal to milligrams per litre.


Parts per thousand, equal to grams per litre.


Protects filters from damage by preventing the intake of objects, which are too large and also intended to protect fish from being trapped in the filter.


A one-celled organism (protist) similar to an animal; example: ich.


Abbreviation for parts per million, a measurement used in test kits.



Quarantine tank

A tank set up for newly acquired or sick fish to isolate them from the main aquarium until they can be safely introduced.

Holds fish temporarily apart from others for assessment.




ORP or Redox potential is a measurement of water purity and of a systems ability to break down organic waste. The measurement is expressed in millivolts by an ORP monitor.


Synthetic media used for chemical filtration through a process known as ion-exchange.

Reverse Osmosis

A process of filtering tap water for use in the aquarium. Water passes through a membrane which filters out all elements leaving the water very pure. Trace elements you want will have to be adjusted as well as the pH 


Microscopic animals which are an important food source for fish.




The measurement of dissolved salts in the aquarium water. 

The measurement of the amount of dissolved salts in seawater.


A disease caused by bacteria growing in the blood (see Ailments).


Physiological response to stress or injury.

Soft water

Water with a low concentration of dissolved salts.

Water with dissolved solids which are less than 100 ppm.


To release eggs and sperm into water.

Specific Gravity

The measurement used in marine systems to determine salinity.


Genetically distinct population(s) that interbreed but are reproductively isolated from other such groups.

Species tank

An aquarium where only one type of fish is kept.


Used to describe the wavelengths of light produced by a bulb.

Sponge filter

A large foam rubber block connected to an air lift tube. Water is drawn through the sponge, which acts as a mechanical filter and a bacteria colony. Especially useful in breeding or fry tanks. 

A filter for small tanks made of plastic foam which traps tiny particulate matter, but mostly provides surface area for the growth of helpful bacteria.


A line of fish developed which differentiates from the original species with its own genetic pattern, colour and other tendencies; ex. Purple Delta Guppies as upposed to Red Delta Guppies.


The material used to cover the bottom of the fish tank.

Material (sand, gravel etc.) placed on the bottom of an aquarium.

Submersible heater

A device that raises the water temperature, which can be completely covered by water safely.


The process whereby a female stores sperm and can produce numerous broods without further impregnation.


Sulfuric salts in water. They form what is known as non-carbonate hardness.

Swim Bladder

A thin-walled, gas-filled sac found in bony fish that permits them to control their buoyancy and thus rise or sink in the water.


A term used in judging referring to the overall pleasing appearance of the show fish (for example) in the proper proportions including colour, body, dorsal and caudal shapes.



Trace elements

Minute substances found in water,that are needed for proper plant and fish growth. Usually replenished with partial water changes.

Trickle filter

A wet dry filter using a drip plate to disperse the water over bio-media. 

A water purifier in which water flows slowly, or trickles, over media not submerged but held in a tray or chamber, meant to facilitate attachment and growth of nitrifying bacteria.

Turnover rate

The number of times the water in an aquarium is passed through the filtration system in one hour. The minimum should be three or four times per hour




Ultraviolet light, generally not wanted in the aquarium. Special filters or shields are required for its' use.

Ultraviolet sterilizer

A unit designed to kill parasites and disease causing bacteria with ultraviolet light.

Under-gravel filter

A type of filter placed under the substrate that utilizes an air pump or power head to pull water through the gravel and thus oxygenates the bacteria to help in the nitrogen cycle. Not recommended for live plant tanks.

A device for enhancing bacterial nitrification in substrate, made of a slotted plate which is placed under the substrate.

Urogenital opening

The common outlet of excretion and reproduction systems in fish.



Ventral fins

Paired fins on the lower part of the fish, located below the gill covers. Not all fish have these. The pelvic fin.


A valve which makes bubbles by drawing air into fast flowing water. Especially useful in protein skimmers. 

VHO lights

Very High Output: florescent bulbs with a much higher output than NO bulbs, they require special ballast and end caps, mostly used on freshwater plant tanks or marine reef tanks.


Any micro-nutrients needed for continued good health of an organism. Many products are sold for specific animal.

Giving birth to live young.



Water properties

Elements used to determine water quality. Total hardness, carbonate hardness, pH, ammonia, nitrate and temperature are the most used indicators.

Wave maker

An electronic device that alternates power to different powerheads to simulate wave motion.

Wet-Dry filter

A type of filter which has a portion of its media exposed to the air with water flowing over or through it, to greatly increase the oxygen content to the bacteria.


A small worm used as food available either live or freeze-dried.  





Yolk sac

A small container still connected to the baby fish after hatching, consisting of the unabsorbed egg yolk.




Refers to the barred pattern or zebra-type pattern of 2 to 5 vertical dark pigmented stripes on the peduncle area of the fancy guppy, expressed only in males which is carried by a dominant gene.


A substance used in fresh water aquaria for the removal of ammonia.


Tiny animals or larvae of other animals living in water. usually used in reference to marine aquaria.