C - Aquarium Dictionary

Updated August 12, 2019
Author: Mike - FishLore Admin
Social Media: FishLore on Social Media

Aquarium Fish Definition and Glossary

abbreviation for Chinese Algae Eater.

Calcium :
Ca, is an element needed by corals, clams, snails, and certain algae and invertebrates to grow. Natural Saltwater has a range of approximately 380 - 450 mg/L and it can be difficult to keep this level up in an aquarium with calcium consuming corals, clams and algae. There are various ways to keep the calcium levels up. Some popular ways include the use of Kalkreactors that dose kalkwasser and Calcium reactors to dose calcium. You can also purchase diluted calcium chloride on Amazon (easier but kind of expensive) and dose that way. The problem with dosing liquid calcium is that you have to also use a buffer (carbonate or bicarbonate) when you dose calcium or you risk lower the alkalinity levels. There are two part calcium/alkalinity solutions and you should look into these products if dosing this way interests you. See:
Calcium on Amazon

Calcium Carbonate :
CaCO3, a main component of many rocks, seashells and crushed corals. Saltwater reef tank keepers have to dose or supplement this compound in order for corals to grow. Corals need calcium carbonate to grow. See:
Seachem Carbonate on Amazon

Calcium Reactor :
a somewhat complicated piece of aquarium equipment that is used to supplement calcium in saltwater aquariums. A media such as aragonite is mixed with carbon dioxide (CO2) in a tube like device which causes the aragonite to slowly dissolve thereby releasing calcium and other important trace elements which is then dosed into the tank. Aragonite dissolves at a lower pH and the carbon dioxide is used to lower the pH. A calc reactor is sometimes used in tandem with a pH controller.

Candy Cane Coral :
see Candy Cane Coral

Canister Filter :
is an external aquarium filter that pulls water from the aquarium, forces it through various types of filtering media and then pushes the clean water back into the aquarium. Canister filters allow you to use multiple media types inline. For example, these filters often have multiple media trays. In tray one you could use filter floss to remove debris, in tray two you could use activated carbon and in tray three you could use another media type such as zeolite to remove ammonia. These filters are often more expensive than other filter types. A decent, less expensive canister filter: Cascade Canister Filter and another good one here:
Canister Filter
Canister Filters on Amazon

Captive Propagation :
is the process of breeding, growing and raising plants, animals and fish in captive conditions (fish in aquariums) for the purpose of increasing the population of the particular plant, animal or fish.

Catfish :
is a type of fish that is scaleless, has barbels and is often times a bottom dweller. Some stay on the small side such as corydoras whereas others grow to be quite large like the Iridescent Shark. There are both freshwater and saltwater catfish species. Also see: Aquarium Catfish Species.

Carnivore :
an animal, plant or fish that primarily eats meat or meaty items.

Caudal Fin :
is the tail fin on a fish. It is for propulsion. Also see: Fish Anatomy.

Caudal Peduncle :
is the area directly before the caudal fin (tail fin). Also see: Fish Anatomy.

Caves / Coconut Cave :
Caves are used to help fish feel more secure in the tank with the hopes that this will actually make them be more out in the open knowning that they can dash back into cover if necessary. The coconut caves are quite popular with Betta keepers. See more below:
coconut cave
Coconut Caves on Amazon

Ceramic Rings :
is a biological filter media that is very porous and is able to house lots of beneficial bacteria. They are usually placed in filter bags and ran in canister filters or fluidized reactors and should be rinsed in aquarium water periodically. More below:
Ceramic Rings
Ceramic Rings on Amazon

abbreviation for Compact fluorescent Light or Compact fluorescent Lamp. See Power Compact Light.

Chaetomorpha :
is a algae that grows in saltwater and is used by saltwater hobbyists in a refugium. Chaetomorpha is one of the better types of algae for hobbyists to use for nutrient export. Chaeto is often used in an attached refugium where it grows quickly as it consumes and competes for nutrients with less desirable forms of algae. After it reaches a certain density or size it can be cropped and removed from the system, providing nutrient export.

Characin :
one of the fish families that consists of tetras. Also see: Characin Species - Tetras.

Check Valve :
is a one way directional valve used with air pumps to prevent tank water from back siphoning through the air line and destroying the air pump and possibly causing other electrical issues. Use these check valves in all of your air pump lines! They are vey inexpensive and can prevent a disaster. More below:
Check Valve
Check Valve on Amazon

Chemical Filter :
is an aquarium filter type that removes dissolve nutrients from the water. The most common form of chemical filtration in the aquarium is using activated carbon. Also see: Aquarium Filters.

Chemiclean :
an aquarium supplement made by Boyd Enterprises that is used to remove cyanobacteria in both freshwater and saltwater aquariums. They claim that it is safe for all fish, corals invertebrates and the nitrifying bacteria. See here:
Chemiclean on Amazon

Chloramine :
NH2CL, chloramine is used as a disinfectant in tap water. Most municipalities use either Chlorine and/or chloramine to treat drinking water. These chemicals are harmful to fish and must be neutralized in our aquariums before adding fish. Use a dechlorinator like the following to remove or neutralize chloramines:
Seachem Prime on Amazon

Chiller :
is a device that works like a refrigerator and is used to cool the aquarium water. These are external devices and can be quite costly to purchase and operate. For more info, see the Aquarium Chiller article. Also see:
JBJ Chiller on Amazon

Chlorine :
element Cl, chlorine is used as a disinfectant in drinking water. It is very toxic to fish and must be elimated from the aquarium water before use. Chlorine may dissipate if you let the water sit for a day or two, but chloramine may stay in solution. Use a water conditioner that removes both chlorine and chloramine to be on the safe side. Use a dechlorinator like the following to remove or neutralize chloramines:
Seachem Prime on Amazon

Christmas Moss :
an aquarium plant used for building moss walls or carpets. It is considered a hardy and easy to care for plant.
Christmas Moss
Christmas Moss on Amazon

Cichlid :
is a fish from the Cichlidae fish family. They originate from many different locales including Central America, South America and Africa. There are many species and they can sometimes have very different water parameter requirements. Most are great parents to their young and they can become quite aggressive with tank mates while breeding. For more info, see Cichlids profile pages.

Circulation :
refers to the amount of water movement within the aquarium. Water movement is accomplished by using internal pumps (power heads) and/or external pumps. Water circulation is very important and is often too slow in most tanks. High water movement within the tank can help increase the dissolved oxygen levels by increasing surface agitation and it can keep detritus suspended in the water column for the mechanical filter to pick up.

Cleanup Crew :
a term for saltwater aquariums, refers to the algae and detritus eating organisms such as snails, crabs, starfish and sea cucumbers. The need for all these animals in the same aquarium is sometimes debated. Sand sifting starfish can make short work of a sand beds, sea cucumbers can release toxic compounds that are harmful to fish and crabs can kill snails for their shells and pick at sessile invertebrates. Some reef keepers like to keep only snails for these reasons.

Clove Oil :
using clove oil is currently considered one of the most humane methods for euthanizing a sick fish. Proper clove oil use can be found in this thread. See:
clove oil
Clove Oil on Amazon

Cnidarian :
is the term for an invertebrate that has stinging cells called nematocysts. Examples of cnidarians are corals and sea anemones.

CO2 :
carbon dioxide, this is a byproduct of fish respiration and it also sometimes bubbled into freshwater planted aquariums to increase the growth rates of plants in brightly lit aquariums. See:
CO2 System
CO2 System on Amazon

CO2 System :
a carbon dioxide dosing system that bubbles water into freswater aquariums with plants. In brightly lit aquariums there is sometimes not enough CO2 present in the water from fish respiration and it needs to be added (bubbled) into the tank in order to get better growth rates from aquarium plants. See:
CO2 System
CO2 System on Amazon

Cobalt Aquatics :
is an aquarium product manufacturer. They make heaters, filters, aquarium vacuums and fish food for various fish species. Link to their popular Neo-therm heater below:
Cobalt Neo-therm Heater
Cobalt Heater on Amazon

Colony :
on the forum this word is often used in reference to beneficial bacteria for the nitrogen cycle made by ATM. More below:
Colony Bacteria
Colony on Amazon

Conspecific :
belonging to the same species.

Copper :
in measurable amounts, copper can be deadly to a lot of invertebrate species. You can use something like coppersafe or cuprsasorb to remove any copper or heavy metals from your aquarium water. Copper is also used to treat diseases in fish. If you need to remove copper from your tank quickly, see cuprasorb below:
Cuprasorb on Amazon

Coldwater Fish :
are fish species that need to be kept in water temperatures that are cooler than what tropical fish species need. Coldwater fish usually need to be kept in tank water under 70°F (21°C). Goldfish and Koi are good examples of coldwater fish species.

Commensalism :
a form of symbiosis in which one organism benefits from the association but the other organism is unaffected.

Coral :
aside from being a pretty color, a coral is an animal in the class Anthozoa that has colonial polyps and produces a calcium carbonate shell.

Coralline Algae :
is a plant form, or algae that needs light and calcium to grow. Encrusting coralline algae can form beautiful shades of purple or pink and will spread over the surfaces of live rock and on tank walls and aquarium equipment. There are bottled products you can buy now that helps speed up it's growth. See
Purple Up
Purple Up on Amazon

Corallivores :
Fishes that primarily eat corals, the Parrotfishes for example.

Corner Filter :
is an aquarium filter that is placed inside the tank, in a corner, imagine that. A corner filter can provide very basic filtration for an aquarium. Often these are one of the first filters young hobbyists (used to) gain experience with. Also see:
Corner Filter
Corner Filter on Amazon

Crushed Coral :
is an aquarium substrate that helps increase the buffering capactiy of aquarium water. It is made out of aragonite and it actually not crushed at all, but screened to size. Carib Sea Crushed Coral on Amazon is a popular brand with hobbyists. See:
Crushed Coral
Crushed Coral on Amazon

Crustacean :
is an invertebrate with a hard exoskeleton. Examples of crustaceans include lobsters, crabs and shrimps.

Cryptocaryon :
this is more commonly known as marine ich or saltwater ick. It is a parasitic infection with very small salt like spots that show up on the body of the fish. It can be deadly to the fish and once you can see these white spots, the infection is in the advanced stages. Prompt action may need to be taken and there are many fish medicines on the market to treat this infection. Also see: Saltwater Fish Disease.

Cryptocoryne :
Cryptocoryne Wendtii - an aquarium plant that is moderately difficult to keep. They need moderate lighting levels. More here:
Cryptocoryne on Amazon

Cuttlebone :
derived from cuttlefish, cuttlebone is used in aquariums because as it dissolves in the tank it releases calcium and other minerals that snails can use for their shells. See:
Cuttlebone on Amazon

Cyanobacteria :
considered a nuisance in saltwater aquariums, this is a bacteria that is more commonly called "Red Slime Algae". It is primarily caused by low water flows, high amounts of dissolved nutrients and maybe an incorrect spectrum of lighting. Increase water flows, use a protein skimmer, increase the frequency of water changes, limit nutrients, replace old lights and use Reverse Osmosis or Deionized water for top-offs and water changes. Hobbyists also use Chemiclean to remove cyanobacteria in both freshwater and saltwater tanks:
Chemiclean on Amazon

Cyprinid :
is a type of freshwater fish. Also see Barbs - Cyprinids.