Aquarium Glossary


Aerobic : Organisms that need oxygen to survive. When organisms need oxygen to survive they are called aerobic.

Acclimatization: Getting fish used to a new environment like new tank conditions.

Acidic : When the pH of your fish tank water is under 7.

Actinic Light :A type of tank lighting that uses blue wavelengths and is able to expand farther than other light sources.

Activated Carbon : A substance that is used to clean aquarium water, especially decaying food.

Air Pump : An air pump is a device used to pump air into your aquarium via a rubber tube.

Air Stone  : A decorative synthetic stone hooked up to the air pump tubing.

Aeration : The process of adding oxygen to your tank using items like air pumps and air stones.

Algae : A simple flowering plant that can build up in aquariums and (usually) should be removed during cleaning.

Alkaline : Opposite of Acidic – when the pH of your tank water is over 7.  Also referred to as basic.

Anal fin : The fin on the bottom of the fish, between the anal opening and the tail fin.

Aquarium : A glass or plastic container manufacturers to hold water and aquatic creatures and plants.


Background : The backside of your tank. There are prints that you can use to make the background more interesting.

Ballast : A device used in regulating power and running your fluorescent lamps.

Bio-balls : Placed in filters that promote bacterial growth and help with the nitrogen cycle.

Biological Filtration : Meaning that bacteria aid in the filtration of the aquarium water.

Bottom Feeder : A species of fish that, as the name implies, spends time scavenging along the bottom.

Brackish Tank :A tank that is neither a saltwater or freshwater tank, but set up to replicate environments where freshwater meets saltwater.

Breeding Tank : A specialized aquarium that is set up for the breeding of fish.

Brine Shrimp : A type of fish food, sometimes fed to fish to prepare for spawning or breeding.

Brood Stock : A pair of fish used for breeding.

Buffer : A chemical used to change the alkalinity of the water.


Carnivore : An organism that primarily eats meat.

Caudal Fin : The tail fin of a fish

Chemical Filter : An aquarium filter that removed dissolved nutrients. An example is activated carbon.

Chloramine : A disinfectant used in tap water that must be combated with another chemical to dispellit in aquarium water.

Chlorine : Similiar to Chloramine, must be neutralized when using tap water in your tank.

Circulation : The movement of water throughout your aquarium.

CO2 : The abbreviation for carbon dioxide, a byproduct of the respiratory process of the fish.


Dechlorinator : An additive that is used to eliminate chlorine and chloramine from regular tap water to make it safe for your aquarium fish.

Detritus : The substances that give off Ammonia, namely fish waste and uneaten, decaying food.

Dorsal Fin : The fin or fins located on the top of the fish.


Ecosystem : An environment, and all of the living things that make up the environment and their relationship with it and each other.


Filter : A device to clean the aquarium water; can be mechanical or biological, or sometimes even chemical.

Fry : Free-swimming fish young.

Full Spectrum Light :A light that displays the whole spectrum of visible light, light the sunlight.


GH : General Hardness – the hardness of your water.

GPH : Gallons Per Hour – the measurement of a filtration system’s turning over of water.

Gills : How fish extract oxygen from the water.


Habitat : Where your fish normally lives – for example: freshwater habitat.

Heating System : Aquarium equipment used to heat the water. The term ‘Heating System’ usually refers to the heater and thermometer. There are many types and varieties of aquarium heaters on the market and it can be a good idea to invest in two lower wattage heaters instead of one higher wattage heater in case of heater malfunctions.

Herbivore : An organism that primarily eats plants.


Ichthyology : The study of fish




Kelvin : A scale used to measure color temperatures of light used in aquariums.


Larvae : The first stage of a baby fish. Larval forms often look different than the adults.

Live Rock : Rock that is inhabited by beneficial bacteria.

Live Sand : Sand in a saltwater aquarium that is inhabited by beneficial bacteria.


Marine Biology : The study of ocean life.

Mechanical Filter : A filter for your aquarium that is not biological or chemical.


Nitrate :  What nitrite turns into at the end of the nitrogen cycle.

Nitrite : What ammonia turns into at the middle of the nitrogen cycle.

Nitrogen Cycle : Ammonia from fish waste and decaying food turns into ammonia, which bacteria consume and turn into nitrite, which also get consumed and turned into nitrate, which must be removed by changing out the water.


Omnivore : A fish that eats both meat and plants.

Oxygen : The air we breathe – and the air fish breathe, although it is pulled from the water through their gills.


pH : The measurement of water that will tell you if it is considered neutral, alkaline or acidic. Under 7 is acidic and over 7 is considered alkaline.


Quarantine Tank : An aquarium that is used for keeping new fish to make sure they are healthy before putting them in with your general population, or a tank that is used for sick fish until they recover.


Reef Tank : A type of marine tank used to keep saltwater coral and invertebates.


Salinity : The measurement of salt in your marine aquarium.

School : A group of fish that travel together. i.e. a flock of birds, a school of fish.

Spawn : Fish offspring, or the period of time in which fish give birth to offspring.

Sponge Filter : An internal filter that is very easy to maintain. It is both a biological and mechanical filtration system.

Substrate : The bottom surface of your fishtank, usually consisting of gravel, or of sand or mud in marine tanks.

Sump : An aquarium connected to the main one that is used to increase the volume of the entire system and might be used to hide equipment.

Symbiosis : When two different life forms work to help each other.


Temperature : How hot or cold your aquarium water is.

Trace Elements : Elements that are present in only tiny amounts, compared to other elements in the water.


Ultraviolet Sterilizer : Uses ultraviolet light to sterilize the water against harmful parasites.

Under Gravel Filter : A filter designed to be underneath the substrate, out of sight, usually with rising tubes in the corner.




Water Pump : Used to move water throughout an aquarium. External water pumps are used to pull water from the aquarium and send it to sumps or refugiums. After the water passes through the sump or refugium it is pushed back into the tank. Water pumps are also used in closed loop circulation systems that are designed to increase the water movement within the aquarium.











Zooplankton : Tiny organisms that are eaten by many marine animals.