Dictionary of fish keeping terms

Acclimitise or Acclimitize:
Acclimitisation is the gradual process of introducing fish into a new aquarium. This is done by slowly altering the temperature, ph, hardness and possibly other chemical water parameters to minimise stress.

Is a measurement of water, where the ph is less than 7.

this is a clear resilient plastic material used to construct fish tanks, filters and other devices. It is more transparent than glass and much lighter. However, it scratches easily.

Actinic Light:
actinic lighting is a fluorescent tube that gives off light in the blue and violet wavelength range just below the ultraviolet range.

Activated Carbon:
is a form of carbon that removes dissolved substances from water. Must be replaced regularly as it becomes fully absorbed after a set time.

Adipose fin:
a small fin between the dorsal fin and the tail fin. Not all fish have such a fin but some Characins do.

Aerobic – Utilising or living in air or oxygen. Is used mostly when discussing bacteria

Air Pump:
An aquarium air pump is a device usually with rubber diaphragm used to force air into aquarium tubing in order to pump air underwater.

Air Stone:
Is a block or stone that splits a single stream of air from a tube into a hundred streams of tiny bubbles under water.

Usually when referring to the pumping of air into the aquarium where a current is created by the rising bubbles.

Air Bladder:
An organ in the fish that holds air. It compresses and decompresses the bladder in order to rise or sink in the water.

Microscopic plant-like organisms that can float in water or attach themselves to rocks and other surfaces under water. They are usually green but there are also brown, red, and blue-green forms.

Algal Bloom – A spontaneous overgrowth of algae which turns the water green and cloudy. This is usually caused by an excess of nutrients and sunlight in the water.

Is a chemical used to kill off algae. However, it may also harm plants and other life in the aquarium or pond

This is where the water when measured has a ph over 7

(NH3)is a gaseous compound which forms in the aquarium from decaying matter such as fish food or fish waste products. Ammonia is harmful to fish and displaces oxygen in the water.

a tiny scavenging crustacean that is a food source for many aquarium fish and invertebrates. They can range in size from 1 – 340 mm, but in aquaria are usually less than 50mm. Saltwater aquarium keepers sometimes utilize a refugium to culture amphipods.

this is a chemical used to remove chlorine from tap water. Chlorine is poisonous to fish

the saltwater version of velvet disease.

Anabantid – an air breathing fish that as well as gills has a labyrinthian lung to assist in breathing air.

Anadromous – A fish that is born in fresh water and swims to the sea as an adult

Anal fin:
the anal fin is underneath the fish, between the anal opening and the tail fin.

Living without the need to breathe free oxygen.

Is a vertically flattish fish with elongated vertical fins and refers to either the freshwater angelfish or the marine angelfish

Where there is little or no oxygen in the water, such as in the deeper levels of the aquarium substrate.

A container made from glass or acrylic used to hold and view fish, plants and other aquatic life

is the process of decorating or arranging the items in an aquarium and includes plants, rocks, corals, sand/gravel, and background.

Derived from the shells of coral and other marine creatures mostly consisting of calcium carbonate. Crushed Aragonite sand is an excellent substrate in the aquarium used to raise ph and hardness.

brine shrimp.

Astaxanthin – Carotenoid pigment supplement and antioxidant added to fish food to enhance reds, oranges, and yellows in fish. It can also be purchased separately as a powder additive.

A German word for the tiny crustaceans, insect larvae and other invertebrates found living in algae and other surfaces.

is the backside of the aquarium when it is painted or has some material attached to it usually an underwater scene or even black.

in an aquarium these are small, waterborne microscopic organisms that are present in the water. Some are harmful, but some are beneficial and process toxic waste matter and convert it to safer substances.

is an electrical device used to start fluorescent lamps and for regulating the power flow through fluorescent lights.

is a popular tropical freshwater fish with several species. Aka Cyprinids.

Bare Bottom:
a term used when referring to an aquarium lacking a substrate. Bare bottom tanks are used to try and keep a clean tank for fish species that don’t tolerate waste well

means the bottom of a body of water. Benthic dwelling organisms can live on or in the aquarium substrate.

aka Siamese fighting fish – is a type of tropical freshwater fish and is a member of the anabantid family.

these are small plastic, porous balls that are usually placed in wet/dry trickle filters that because of their large surface area sustain a large population of bacteria that digest waste matter

Bio-load or biological load:
the level of waste matter in the aquarium that the biological filter has to cope with. An overstocked tank will place an excessive bio-load on the filter.

Biological Filtration:
Is now recognised as a crucial process in an aquarium that enables fish and other living creatures to live indefinitely in an aquarium with polluting themselves in their own waste matter. In the aquarium this is achieved by using a filter with a large surface area and a high flow of water through the filter. The bacteria that grow in the filter digest and process the waste matter into relatively harmless substances.

A slimy film of bacteria that adheres to a surface that digest waste matter such as ammonia into nitrites and nitrites into nitrates. Biofilm covers all surfaces exposed to water but mostly tends to build up in the filter where waste matter accumulates.

An accurate aquarium simulation of a naturally occurring underwater scene.

Black Water Extract:
is a water conditioner that contains peat and it helps to acidify water for aquariums. Aquarists keeping fish from the Amazon river may be interested in using black water extract with rain water to more accurately re-create Amazon river water conditions.

a water based filter feeder. this is the red, worm shaped larvae of the midge fly. They can be found in the bottom of streams and ponds. They are high in protein and can be given as a treat to fish or to help condition them for spawning.

Tubifex Worm.

Sometimes called Malawi bloat. It is caused by a proliferation of protozoan parasites in the intestines. It is sometimes fatal. This leads to a loss of appetite, long white feces and a swollen abdomen. Common in Malawi cichlids, especially mbuna.

Bogwood – Wood that has spent a long time in a peat bog with much the same properties as peat.

Bottom Feeder:
is a fish that spends most of it’s time scavenging the gravel for food. Many catfish and loach species are bottom feeders. They usually have a flat, or wedge shaped body or eel like body.

Brackish Tank:
Is a simulation of the water conditions in the estuary of a river where the river flows into and mixes with the sea. It is made by using lower dosages of sea salt in the aquarium than a marine aquarium.

Breeding Tank:
This is an aquarium set up for breeding fiah and to raise the resulting fry. They are usually set up as bare bottom tanks with sponge filters.

Brine Shrimp:
A saltwater shrimp that is commonly used to feed fish. Newly hatched brine shrimp is an excellent food for young fry. Brine shrimp are easy to hatch from shop purchased eggs by placing them in salty aerated water at about 75F.

Brood Stock:
a fish or a fish pair that is used for breeding. Some fish species pairs (Discus fish) can fetch high prices.

Bubble Nest:
is a nest of air bubbles coated in fish saliva created by the anabantid fish species for protecting the eggs. Mating occurs underneath the nest with the male placing the fertilised eggs into the nest. After mating has finished the male chases away the female and then stands guard underneath the nest for several days until the eggs hatch.

is a powder or chemical used to stabilise the alkalinity of aquarium water so that it can resist changes in pH. These buffering agents usually consist of various carbonates and bicarbonates. Only some of the chemical dissolves at a time. When acidifying agents occur they are neutralised by more of the buffer dissolving. Baking soda can be used as a buffer.

Ca, is an element needed in the skeleton and shells of corals, clams and invertebrates. Sea water has an adequate amount for sealife. However, in the closed environment of an aquarium it gets depleted by the inhabitants’ growth. The marine aquarium needs regular dosing of calcium to maintain sufficient calcium

Calcium Carbonate(CaCO3):
CaCO3, a main component of many rocks, sanils, shells and corals. Saltwater reef tank keepers need to maintain the levels of this important compound so that corals can grow and thrive.

Calcium Reactor:
Used in marine aquariums to help dissolve the calcium in aragonite into the seawater to maintain Calcium levels.

Canister Filter:
is a filter that pulls water from the aquarium, forces it through a filtering medium and then pumps the filtered water back into the aquarium. Canister filters contain various media types. External canister filters are quite large and have an inlet and outlet pipe while internal canister filters are quite small.

Captive Propagation:
is the process of breeding and growing plants, animals and fish in captivity for the purpose of increasing the wild population of the particular plant, animal or fish. This is usually when the species is in danger of extinction.

an animal including fish that primarily eats meat, ie other animals

A fish born in the sea but swims or travels to fresh water where it grows to adulthood. One example is the common eel.

is a type of fish that is scaleless, has barbels and usually a bottom dweller. There are freshwater and seawater varieties.

Caudal Fin:
is the name of a fishes’ tail fin. Most fish use the tail fin to propel themselves forward.

Caudal Peduncle:
is the base of the tail fin.

is a poular algae that grows in marine aquaria
usually in a refugium. Chaetomorpha is better than other macroalgae because it is easy to grow and easily cropped while preventing less desirable forms of algae taking hold. It also is host to many small food organism that can be fed to fish.

A family of fish that includes the tetras

Refers to a chemical compound where a usually inorganic metal such as iron is bonded to an organic compound. This facilitates the digestion of iron or other trace elements by organic creatures such as plants and animals.

Chemical Filter:
is an aquarium filter type that removes dissolved chemicals from the water. Usually using activated carbon.

is a regrigeration unit that cools aquarium water.

NH2CL, chloramine is a compund of ammonia and chlorine used to disinfectant tap water. Chloramine is toxic to fish and must be removed from the water before using for fish.

(Cl) chlorine is used to disinfectant tap water. It must be removed from the water before use. Chlorine may evaporate if you let the water sit for a day or two, but chloramine takes longer to evaporate. Use a water conditioner that removes both chlorine and chloramine immediately to be on the safe side.

is a family of fish. They occur naturally mostly in the Americas and Africa. There are many species and each has its own water parameter requirements. Most show extensive parental protection to their young and they can become quite aggressive with tank mates while breeding. They typically display a lot of social interaction.

refers to the motion of water around the aquarium. Circulation is achieved by the use of internal or external pumps. A high level of circulation within the tank can help increase the oxygen levels in the water by increasing the amount of water exposed to the air. It also disturbs detritus which can then be mechanically filtered.

Clamped Fins: When a fish holds closed its fins. It is a sign of sickness or distress or submission to a more dominant fish.

Cleanup Crew:
In marine aquaria this is when an aquarist has creatures that eat up waste organic matter and algae. Examples are crabs, snails, starfish and shrimps.

Clutch: All the eggs deposited by the female in one spawning.

carbon dioxide is what fish (and plants at night) respire into the water and plants absorb under light. Sometimes CO2 units bubble gas into an aquarium to increase the growth rates of plants in brightly lit aquariums.

Coldwater Fish:
are fish species that originate from temperate climates as opposed to tropical regions. They are most comfortable at temperatures below 70f. Goldfish are the most common example.

a relationship between two organisms in which one organism benefits from the association but the other organism is unaffected.

Community aquarium: An aquarium with several species of fish that peacefully co-exist.

belonging to the same species.

a coral is a marine invertebrate of the class Anthozoa. They usually live together in tightly packed colonies consisting of many identical polyps. There are reef building corals that secrete calcium carbonate forming a shell.

Coralline Algae:
is a sea algae that needs light and calcium to grow. Encrusting coralline algae will spread over the surface of live rock and other surfaces leaving a purple or pink coating.

Fishes that primarily eat corals, the Parrotfish for example.

Corner Filter:
is a small internal canister filter that is placed in the corner of the aquarium.

Cory: short for Corydoras. Small South American armored catfish that is popular with aquarists. There are many species.

is an invertebrate with a hard exoskeleton. Lobsters, crabs and shrimps are examples.

Marine version of ich or ick. It is a parasitic infection that looks like white dots sprinkled all over the fish. It can be fatal and must be treated quickly with an over the counter medication and raising the water temperature.

A bacterial infection in a marine aquarium (called red slime algae). This is usually caused by poor conditions such as a rise in waste matter and poor filtering.

Cycle: When the nitrogen cycle is complete, ie the nitrifying bacteria have become fully established and are converting all the waste ammonia into nitrates


commonly called water fleas. This is a live fish food that is found in lakes and ponds and are usually red or pink.

Dead Spot:
Any area in the aquarium with poor circulation, either within the gravel or in the water. This can lead to cold areas or areas where waste matter collects.

A chemical that can be obtained from aquarist store. It neutralises chlorine and chloramine form tap water

Deep Sand Bed:
A sandy substrate over 4 inches deep that will create anoxic conditions in which anaerobic denitrifying bacteria can convert nitrates into nitrogen gas. However, they are prone to disaster. If there is too much flow then the anoxic conditions won’t occur and nitrate will not be removed. If too little flow then the anaerobic bacteria will not receive new nitrates and starve. Creatures burrowing in the sand helps to release small levels of toxic gases.

the process of removing ions from water using an ion exchange resin. Helps to purify water.

is a process where nitrates are converted to harmless nitrogen gas. This process takes place where there are anoxic areas in the aquarium inhabited by anaerobic bacteria. These bacteria digest nitrates and give off nitrogen.

Fish rubbish consisted of fish excreta or uneaten fish food that settles into or on the gravel or sand.

organisms (fish and invertebrates) that eat detritus.

When the embryos or eggs of killifish, that are in dried up pond beds, go through a stage of suspended growth or development while they are waiting for the next rainy season.

Diatomaceous Earth:
a very soft rock crushed up to make a soil. The rock is the fossilised remains of diatomic algae. It is the filter media used in diatom filters.

Diatom Filter:
a mechanical filter that uses diatomaceous earth material to filter the water. They are not for long term use because the earth quickly clogs up and needs replacing.

is a type of cichlid from the amazon. It is a disc shaped laterally compressed fish.

is a type of plankton. Some are photosynthetic and these are called zooxanthellae.

When a fish demonstrates by extending all fins and exhibiting vibrant colours, accompanied by special movements of the body and fins. Normally during breeding time, but also when vying for dominance and territory.

Dissolved Oxygen:
Oxygen is dissolved in minute quantities in the water and allows the fish to breathe. Can be measured as ppm

Distilled Water:
Water that has been boiled into steam then recondensed in a different container to produce purified water.

Dither Fish:
Calm fish that are not easily disturbed that reassure other timid or frightened fish that it is safe to come out of hiding and carry on as normal.

is a fish or other creature that is active during the day.

Do It Yourself. Certain aquarium items can be home made thereby saving costs. Repairs are usually DIY jobs also with varying success. There are many online videos describing many DIY tasks

degree of carbonate Hardness measured in ppm

is a rock composed of calcium magnesium carbonate. Sometimes used instead of aragonite. However it is not as good as aragonite in buffering the ph of the water. So aragonite is the preferred choice.

Dorsal Fin:
the fin located on the fishes’ back.

Dosing Pump:
is a pump used to drip feed chemicals into an aquarium on a continuous or occasional basis. Kalkwasser is sometimes dosed using a slow drip dosing pump.

Wood that has been drifting or floating in water. It is often used to decorate aquariums. However it must be made tank safe by boiling.

When there is a build up of fluid in the tissues of the fish that causes the scales to stick out like a pine cone. It is a bacterial infection caused by an excess of fish waste and rotting food. It is usually fatal.

Dutch Tank:
An aquascaped aquarium which is designed to primarily display aquatic plants.

An interconnected system of creatures, plant life and bacteria that occur in a distinct environment together with how they survive alongside each other in the long term.

Egg Burier:
Is a fish where the female lays eggs in soil, sand or gravel

Egg Layer:
Is a fish where the female lays eggs on or in a particular location

Egg Scatterer:
Is a fish where the female lays eggs as she swims in open water.

Egg Spots:
Fish egg-like markings on the anal fin of African mouthbrooder male fish. During mating the female tries to collect up eggs that she has laid as well as the fake eggs but instead gets fertilised by the male.

Endangered Species:
is an organism, animal or fish that is at risk of becoming extinct. The main causes are the population of the animal is dwindling or the habitat of the animal is under serious threat.

means that a fish or animal is native to a particular geographical location and not introduced from elsewhere.

when an organism lives within the cells of another organism.

is an area where a river connects to the sea and is brackish in nature, ie seawater and freshwater mixed.

Euthanise or euthanize:
To painlessly kill a fish that may be injured or ill with no chance of recovering, and put an end to its suffering.

External Filter:
Any filter that operates outside of the aquarium e.g. a HOB filter, or a canister filter.

when a species is no longer living.

Fertiliser or fertilizer:
Nutrient added to the water to feed aquatic plants.

is a piece of aquarium equipment used to clean the aquarium water through mechanical, biological or chemical methods by forcing water from the aquarium through a media.

Filter Media:
Various porous materials used in a Filter to remove particles or chemicals from the water.

Fin Rot:
Is a bacterial infection that affects the fins of fish causing the fins to rot away. May be caused by poor feeding, poor water quality or fin nipping by other fish. If the cause is removed the fins usually grow back.

is a baby, young, or very small fish.

Fish Only(FO):
In marine aquaria where no corals or other lifeforms are used

Fish Only With Live Rock(FOWLR):
In marine aquaria where an ecosystem is created with fishh and live rock. It is usually easier to maintain this set up.


An aquarist. Someone who keeps fish in ponds or aquaria.

Fishless Cycle:
Maturing an aquarium without live fish, using ammonia, or decaying matter. This is done to avoid stressing fish during the maturation process.


Aggressive posturing where a fish will spread out its gills and fins to scare a rival. A prime example is the Betta.

Where the fish have an itch and try to scratch themselves against objects in the aquarium. This may be caused by parasites, chemicals in the water or an excess of ammonia

Floating plants:
Plants that lay on the surface of the water.

fluorescent Light:
is an aquarium light tube that contains neon gas to produce light. These lights need a starter to operate.

Fluidised Bed Filter or fluidized bed filter:
an aquarium filter that forces water through a sand medium causing the sand to churn. As the aquarium water flows continuously through the sand, beneficial bacteria colonise
the sand. Because of the large surface area provided by the grains of sand with the continous flow of water, it is thought to be a very powerful biological filter

A coral fragment. Corals are expensive and aquarists will break off a frag of coral to trade with other aquarists. The frags will grow into full blown corals over time

Frogspawn Coral:
A type of coral

free swimming baby fish. Ie baby fish that have absorbed the yolk sac and have started swimming.

Full Spectrum Light:
is a light that displays the entire spectrum of visible light from violet through to red trying to reproduce sunlight. Sunlight is full spectrum.

a freshwater amphipod that is used to feed fish.

Gang valve:
a valve that is used with air line tubing to split and regulate air flow from a single tube to many tubes.

General Hardness. This is a measurement of the dissolved minerals in aquarium water.

Genital Papilla:
is the white bud through which the sperm and eggs pass on fish during breeding.

in taxonomy it refers to group of similar organisms. For any species it has a genus and a species name. eg betta splendens – genus betta and species splendens

is the most common and popular pet fish. Carassius Auratus derived from the crucian carp.

These are the pink reddish fleshy structures inside the gill plates that extract oxygen from the water

is a modified, rod like, anal fin in livebearers that is used to inject sperm into the female livebearer

is a member of the anabantid family. Also they can breathe air through the use of a labyrinthian lung

Gravel Vacuum:
A siphon made of a large diameter acrylic tube attached to a smaller diameter flexible hose. The vacuum is primed either by pumping or by sucking on the narrow pipe while the large end is in the water. Water will then start flowing out. The large end is then used to hoover the gravel.

Gravid Spot:
The dark spot in a female livebearer’s abdomen where the fry are developing. It becomes larger and darker as the female comes closer to giving birth.

Green Water:
This is when an overgrowth of suspended algae takes place in standing water

Grindal Worm:
Similar to white worms but smaller. Can be fed to smaller fish and fry.

Grow Out Tank:
A tank that will house fry until they become large enough to sell or be placed with other adult fish.

is the environment where an animal, plant or fish lives in the wild.

Hard Water:
is water that has dissolved in it many stone like minerals such as calcium carbonate. It is measured in units of hardness called GH. Some fish prefer hard water while others prefer soft water.

A device that raises and maintains a set temperature. Normally they have an adjustable dial to vary the required temperature and a thermostat that regulates the heater.

is a fish that eats plants or algae.

is a fish or other animal that has both male and female organs for producing eggs and sperm.

HOB Filter:
Hang On Back filter. An External Filter which is hung on the back of the tank.

tank lid that usually houses lighting and has a hatch for feeding

Hospital Tank:
An empty aquarium set up to treat sick, distressed or injured fish. It usually has no gravel or plants. It will have a sponge filter, a heater and some hiding places for the fish and will have subdued lighting. Medications and treatments can be applied without affecting the other fish.

Hybrid Fish:
is the fish resulting from breeding between two different fish species.

This measures the density of water. The more dense the more dissolved solids(such as salt) there is. It is a guide to marine tank keepers to guage salinity

Someone who studies fish scientifically. They may work for public aquariums, museums of natural history, or for universities doing research and writing papers.

Ich or ick:
White spot disease. This is a parasite and is a common fish ailment that is usually caught when the fish have had a chill. It can be lethal if untreated. There are many over the counter remedies at your local pet store. Also raising the aquarium temperature to mid 80F and adding salt will help elminate ich.

Is light created from light bulbs. The light is created by passing an electric current through a wire inside a vacuum or inert gas. When the wire heats up it glows white.

These are microscopic organism that are grown by aquarists to feed young fish fry.

Instant Cycle:
Where the usual long winded process of maturing a filter is avoided. This is achieved by using the bacteria from an existing filter in the new filter.

Internal Aquarium Filter:
any filter that needs to be operated inside the tank. Examples include sponge filter, the undergravel filter, and corner filter.

An aninal that does not have a backbone or internal skeleton but may have an exo-skeleton or shell. Examples are snails, shrimps, and crabs

An element that is used in aquariums as a supplement to ensure there isn’t a deficiency in the iodine level in the aquarium water. The ideal iodine level in marine aquaria is 0.03 to 0.06ppm

In fish keeping terms is used to specify the exact hue of fluorescent tubing or other lighting. Kelvin is a measure of the colour temperature of light. The higher the Kelvin the closer will be the hue to natural sunlight. 3500K or less is amber, 3500-4100K is white, 4200K and over are bluish

A German word meaning lime water, because the germans invented the technique of dosing aquariums with lime water.
Calcium hydroxide is dosed into an aquarium on a slow drip feed. The process can also be automated depending on the ph level of the aquarium and thereby maintaining a stable ph.

Kalk Reactor:
A machine to mix calcium hydroxide into water. It has an automated mixing device as well as a slow drip feeding system.

Carbonate Hardness. A German measurement of the amount of dissolved carbonate ions in water.

A type of fish that reproduces by leaving eggs in the soil that hatch after the pond dries up. When the rainy season comes the eggs hatch out. Male killifish are some of the most colourful fishes known.

Are small crustaceans that look like shrimps and feed on plankton. They are fed to aquarium fish.

Labyrinth Organ:
is a specialized organ in the anabantid species that allows them to take in oxygen at the water surface directly from the air.

When refering to fish, this is when the fry is newly hatched and still has a yolk sac attached. When this is absorbed the fry is no longer a larvae

Lateral Line:
This is a line running along both sides of the fish. It consists of specialised scales with a dot like pit in the middle. These pits detect minute variations in water pressure. The fish can sense vibration and objects in the water through their lateral line

is a type of soil rich in iron and aluminium and are rusty-red in colour they provide excellent fertilisation for aquarium plants.

Is when a fish eats the scales off other fish.

Lettuce Clip:
Is a clip that attaches to the side of the aquarium so that lettuce, seaweed and other vegetable matter can be kept in place while herbivorous fish feed.

Light Emitting Diode. Is a form of bulb where light is emitted when it is activated. It is typically has a very low power consumption and long life.

Light Hood:
tank lid that usually houses lighting and has a hatch for feeding

Limewood Diffuser:
Is an air stone made from wood and operates in the same way creating hundreds of tiny bubbles

A fish that gives birth to free swimming fry such as the guppy, platy, swordtail, molly and others.

Live food:
living insects and worms fed to aquarium fish

Live Rock:
The skeletal remains of coral reef structures and the organisms that live on and in the structure. Because of its highly porous nature it is infested with beneficial bacteria that digest waste matter into less harmful nitrates.

Live Sand:
Sand in a marine aquarium that is populated with nitrifying bacteria, invertebrates and microscopic life forms that breakdown fish waste into harmless substances.

scientific term to denote total brightness across all light wavelengths, ie total output of a bulb.

Light intensity. 1 lux = 1 lumens per square metre.

Lux Meter:
A device that measures light intensity in lux units. Useful in marine aquariums to determine if the lighting is bright enough for corals or a particular species of coral.

Is an abundant element in sea water with a concentration between 1200ppm and 1300ppm. It is vital for marine aquarists to monitor the levels and to top up with magnesium as needed.

Fish from lake Malawi

is a fleshy body structure found in molluscs and in the clam is a cloak like covering that has various functions such as protection from bright sunlight and the epidermis of the mantle may produce a shell.

Marine aquaculture, which is the farming of fish or other sea creatures using seawater, either in open sea or inland where water has been drawn from the sea.

a saltwater aquarium or environment or the sea.

Marine Biologist:
Is a scientist that studies all the creatures of the sea, including fish, plants, algae, plankton, molluscs, corals, even sea mammals, etc

is an African name meaning rock dweller and refers to certain species of fish from lake Malawi that live in the rocks. They are very territorial, protecting their own patch of rocks and spaces between the rocks. They mainly feed off algae and creatures within the algae. They are a favourite fish for many aquarists.

Metal Halide:
This is a special type of lamp that produces a lot more(3 to 5 times more) light per wattage than ordinary incandescent lighting. It does this by passing electricity through a wire that heats up and glows. The wire is in a glass bulb that contains vaporised mercury and metal halides instead of a vacuum.

Fish semen which is sprayed into the water near the females eggs.

Mosquito larvae:
The young of the mosquito that grows in stagnant water and is used as a live food for fish.

Mouth Brooder:
fish that hold eggs and fry in their mouths. Many African cichlids are mouthbrooders. Mouthbrooding occurs in many various species of fish including, mouthbreeding betta, Arowana, geophagus and cardinal fish.

A mash of solid waste materials includin fish excrement, uneaten food, dead plant material, etc

Perfect symbiosis in which both guest and host mutually benefit form the relationship with each other.

Mysis Shrimp:
known as the opossum shrimp. It is a small shrimp like crustacean that rears its young in a pouch and is an excellent food for picky eaters such as the Seahorse.

newly hatched brine shrimp. They are an excellent food for slightly larger fry or newly born fry of larger species

is an explosive stinging spiral cell that sometimes injects poison. corals, sea anenomes and jelly fish used these very complicated structures to sting or puncture, to capture prey or repel an enemy.

This is the resulting chemical from the decomposition and bacterial processing of organic matter. Plants to some extent utilise nitrate, however usually a further means of removal is needed to prevent its build up. This is achieved by partial water changes or having anaerobic bacteria turn the nitrate into nitrogen gas.

This is produced by bacteria that digest ammnonia to give off nitrite. Nitrite is still toxic so needs further processing by different bacteria to produce less harmful nitrate

Nitrogen Cycle:
This is when waste products decay to produce ammonia. Certain bacteria process the ammmonia to produce nitrite. Certain other bacteria process the nitrite to produce nitrate. And finally anaerobic bacteria process the nitrate to produce nitrogen. Therefore the original waste matter has been completely recycled. Not all steps of the nitrogen cycle are present in newly established aquaria. As the process develops, there are spikes in ammonia, nitrate and nitrite levels which aquarist reduce by doing partial water changes.

refers to an animal or fish that rests during the day and becomes active at night.

very nutritious edible seaweed that has been packed and dried for human consumption and is a good food for herbivorous fish.

Nuchal Hump:
is a large hump on the forehead of some male cichlid species. This hump grows larger as the fish matures.

external teeth that grow in the skin, near body openings found on some catfishes.

is an animal or fish that eats both meat and plant foods.

is a parasite that causes velvet disease found in freshwater fish.

Is the process that regulates the dilution of internal fluids. In fish it is the regulation of the internal water content preventing it from being too salty or too diluted. It is achieved by osmosis

This is where substances travel through a semi permeable skin or barrier and there is a slow equalisation of substances on both sides of the barrier. Higher concentrations move to the side of lower concentrations.

A whitish tubule that female fish pass eggs through in the vent.

Is a gas that is vital to life. Most fish breathe oxygen via their gills. Water has a certain level of dissolved oxygen that fish can extract.

is an unstable form of oxygen and can be used to increase the oxygen level in an aquarium. Also can be used in protein skimmers.

An aquarium with an amphibious land area, such as a turtle tank.

A tube that descends from the vent of the male fish in order to deliver milt onto the eggs in order to fertilise them. Only visible during breeding.

This is a type of symbiosis in which the guest organism takes benefit at the harm of the host organism.

Various species of Aulonocare from Lake Malawi

Partially decomposed moss. It has several uses in the aquaria such as acidifying and softening water as well.

Pectoral Fin:
These are the foremost pair of fins and are underneath the fish near the gills. They are used as brakes and for fine manoeuvring.

This is the breeding style of many marine fish. Fertilised eggs are spawned into the water to be carried off on tidal currents.

Pelvic fins:
Are the pair of fins under the pelvis.

is a measure of acidity and alkilinity. The lower the number the more acid the water is. Anything under a reading of 7 is acid while anything over 7ph is alkaline. Different species of fish and plants prefer different ph levels.

Is a compund that is an excellent fertiliser for algae and plants. Algae need it more than plants so reducing phosphate levels can reduce algae.


Sea based algae. Microscopic plant life that floats in the ocean.

is long for oodinium. A parasitic single cell that causes velvet disease.

A fish whose diet is mainly other fish.

Short for plecostomus. is a type of catfish popular in the tropical fish hobby.

is a chamber like area beneath a sand bed in marine aquaria to achieve biological filtration.

Power Compact Light:
This refers to fluorescent lights where the tube is u-shaped or the tube goes back and forth but both electrical ends come back to the same area. Normal fluorescent tubes have their electrical ends far away from each other.

Power Filter:
Filters with an internal pump mechanism. They may be HOB, external canister or internal. They always perform mechanical filtration but may also perform biological filtration.

Power head:
May be part of a filter or stand alone and is a device that pumps a jet of water at force around the aquarium.

Parts per million, is used to measure the amount that one substance is dissolved or distributed in another substance, especially when those quantities are relatively small. Eg oxygen in water.

Protein Skimmer:
In marine aquaria it is a type of filter that removes organic matter from the water by creating microbubbles which bubble up in a chamber of water attracting organic matter. The organic waste coated bubbles flow up and over a funnel where the are collected in an overflow cup. The cup has to be regularly emptied and cleaned. This results in most organic matter being removed before being processed by biological filtration, lessening the burden on the biological filter.

Protogynous Hermaphrodite:
When a species is capable of changing from female to male this is usually triggered in an all female group such as when a male has died. The change may take several weeks to months to complete.

Pulsing Xenia:
Is coral with feathery polyps that pulsate.

Poly vinyl chloride, is a white plastic material used in aquarium piping.

Quarantine Tank:
is like a hospital tank in set being pretty sparse. It is set up to house newly acquired fish to see if they are carrying any illnesses that may only show themselves after several weeks. It also allows observation while the new fish get a chance to acclimitise to the aquarists water conditions

Reef Tank:
Is a marine aquarium that is set up to completely simulated the marine environment and will include the whole range of creatures from that environment. They are more difficult to maintain than fish only set ups and require more intense lighting and filtration. They also need more monitoring and maintaining. They are more expensive set ups and difficult to achieve success with.

is a device to accurately measure the salinity of aquarium water. It uses a prism to do this.

is a separate tank that shares the same water put prevents inhabitants from the main tank entering or inhabitants of the seperate tank leaving. This is a refuge for organisms that would not survive in the main tank.

is breathing for fish this is when they pass water over their gills to extract oxygen from the water

Reverse Osmosis:
This is the process where water is pushed through a membrane that filters out larger atoms and compounds. This results in pure or purer water.

RO Water:
Water that has been passed through a reverse osmosis device that removes impurities creating soft water. RO water can be up to 9 times purer than tap water.

Rock Scaping:
Aquascaping using rocks or in a marine aquarium using live rock

the amount of dissolved salts in water. Measured in specific gravity or refraction.

The grouping behaviour of fish. many small defenceless species of fish group together in schools to try and avoid being eaten.

Immobile when refering to creatures in an aquarium. They are usually physically attached to a surface.

A device such as a tube that sucks water out of an aquarium by the use of gravity. The end of the pipe outside the aquarium must be lower than the level of the water in the aquarium for it to work.

Slime Coat:
A mucuous coating that covers the entire fish. It is slippery to the touch. It has two main uses. It forms a barrier to parasites, bacteria and fungal infections. Its second function is to reduce friction as the fish swims through the water.

For fish this means breed.

Specific Gravity:
A measurement of density or salinity of water. Marine aquaria need a specific gravity reading between 1.021 to 1.025

This is the dried remains of a type of blue-green algae that makes an excellent food for herbivorous fish.

Sponge Filter:
Is a simple type of filter usually powered by an airstone. Water is sucked through the sponge, trapping waste organic matter. This waste matter is then biologically digested by bacteria living in the filter. Despite their simplicity, sponge filters are surprisingly good filters. They are easily maintained. If they should become clogged then squeezing out excess dirt in a bucket of aquarium water is a quick and easy remedy.

A table or framelike structure that supports an aquarium. An aquarium on a stand will be at a convenient height off the ground for viewing, etc.

a trace element in natural saltwater that many marine aquarium creatures require and is naturally present in sea salt mixes.

is the bottom of the aquarium usually consisting of gravel, sand, mud or soil

is a tank connect to the main aquarium. It is a way of hiding unsightly filters, heaters, protein skimmers and other in tank equipment. It is located beneath or behind the main display aquarium and so hidden from sight.

The surgeonfish or tang are a group of marine fish that have a retractable blade at the base of the tail fin. They use this for attack and defense. They can inflict deep cuts on people.

Swim Bladder:
An organ in the fish that holds air. It compresses and decompresses the bladder in order to rise or sink in the water.

is when two different organisms live off each other or one lives off the other. This relationship may be both ways beneficial or just beneficial to one organism and harmful to the other organism.

See surgeonfish.

Target Feeding:
is where you use a syringe or other device to deliver food directly to the mouth of the animal to avoid clouding the aquarium.

is the scientific study of methods used to name and classify living creatures into groups, families and finally into species.

measurement of warmness, either degrees Fahrenheit(F),Celsius(C) or Kelvin(K).

is a group of popular freshwater aquarium fish that is distinguished by the presence of a secondary smaller dorsal fin between the dorsal and the tail fin.

A device to regulate electrical devices so that they can come on and off at times set up by the aquarists. It is especially useful for lighting so that the fish and plants get a sense of dawn and dusk being at the same time everyday.

Trace Elements:
These are ingredients in saltwater that although may be in low quantities are nevertheless required for the health of the inhabitants of the marine aquarium.

a type of marine fish with two dorsal spines. One spine triggers and locks the other spine into place. This is a defence mechanism.

Trickle Filter:
an aquarium filter that has a dry and a wet stage. Aquarium water is trickled over plastic bio-balls (or other porous objects with high surface area). Because the balls are not submersed in water they also are exposed to air. In theory this allows better biological filtration.

These are the small white dots around the gills and pectoral fins of male goldfish and koi when they are in breeding mood.

Tubifex Worm:
is a worm that feeds off waste matter at the bottom of ponds. It is a live food that is fed to fish. However, care must be taken as tubifex may carry disease.

Turn Over:
This refers to the amount of water flow through a filter compared to tank size. Eg a 200 litre per hour filter will turn a 50 litre tank over 4 times per hour

Ultraviolet Sterilizer:
Is a device that passes water through a narrow tube with an ultraviolet light shining on the tube that kills all lifeforms that pass through the tube.

Under Gravel Filter:
A type of internal filter that has plastic plates with holes placed beneath the gravel and tubes with air stones that suck up water from beneath the gravel thereby causing water to flow through the gravel. With a good enough flow biological filtration in theory would take place. In practice the gravel would soon clog up with fish waste and create dead spots that would very quickly pollute the aquarium.

Venturi Valve:
A valve that creates a low pressure area when water passes through a pipe it will suck in air through a small hole. In protein skimmers micro-bubbles are created this way.

Vegetable Clip:
see lettuce clip

Velvet Disease:
is caused by single celled parasitic organisms – Amyloodinium is the saltwater version and Piscinoodinium the freshwater version.

Water Change:
This is the process of removing some water from the aquarium and replacing the water with fresh water. In marine aquarium the newly added water has sea salt added in the right proportion before use. This helps reduce waste matter such as nitrate.

Water Parameters:
refers to ph, hardness, salinity, ammonia, nitrite, nitrate and temperature measurements. This gives the aquarist a guide as to the condition of the water.

Water Pump:
is an electrically powered device that propels water.

Wave Maker:
This is a device to simulate waves in an aquarium to create a more natural environment for marine fish or large lake fish.

Wet-Dry Filter:
This is a biological filter that alternates between having the filter media exposed to air and exposed to water. In theory it is supposed to increase the amount of aerobic bacteria to boost the filter’s biological capacity. However, this may not be the case because there is sufficient oxygen dissolved in water for such bacteria’s needs already

White Spot Disease:
see Ich.

X-Ray fish or X-ray tetra
Pristella maxillaris, is a tetra with a see through body hence the name.

This is used as filter media. It chemically filters out ammonia from water

Plankton are microscopic organisms that float in seawater. They may be plantlike or animal like.

is an algae that lives within the cells of various corals. They provide corals with carbohydrates which the zooxanthellae derive from photosynthesis. While the corals provide shelter and basic nutrients for the algae to grow.

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