AQUATIC TERMINOLOGY

Absorption: The process by which filter media attracts unwanted molecules to its surface via a chemical charge.
Acidic: Water with a pH of less than 7.
Acrylic: A plastic material used to construct fish tanks, filters and accessories.
Actinic Lights: Actinics are a type of fluorescent light that is very blue. This is the color of light that is most useful to the chlorophyll in marine life, and is the color of the sea below 10 meters.
Activated carbon: A commonly used chemical filter media.
Adventitious root: A root which develops from the node of a stem or similar organ, such as a Rhizome, Stolan or runner.
Aerobic: A term used to describe an organism that needs oxygen to survive. 
Air Pump: A pump which supplies air for lift tubes, skimmers, bubblers, etc. The most common type are diaphragm pumps, though cylinder pumps are available for large installations.
Airstone: A device that attaches to the air pump to create various bubble effects.
Algae: Plant-like organisms which grow in water. While many algae grow as a fuzz or slime without much visible structure, some is leafy. Other algae is hard and calcareous.
Alimentary canal: The tube of the digestive system through which food passes, where digestion takes place.
Alkaline or Alkalinity: Also known as Basic. Water with a pH between 7 and 14. It is commonly measured as carbonate alkalinity or total alkalinity, and is expressed in meq, dKH, or ppm of C⁰³ ions. This is the measure of a solution's resistance to changes in pH. The alkalinity can be raised by adding a buffer.
Ammonia (NH³): A dissolved gas that even in low concentrations is toxic to fish. It is produced by the breakdown of organic waste products. NH³, this is one of the steps in the nitrogen cycle. 
Anaerobic: A term used to describe an organism that lives in an environment with little or no oxygen. Refers to an area where there is no dissolved oxygen in the water. While necessary for some things such as bacterial reduction of nitrate to nitrogen, these areas can also produce hydrogen sulfide and other undesirable substances.
Aragonite: The substance that makes up coral skeletons and coral sand. It's a form of CaC⁰³.
Artemia: Known as brine shrimp.
Auxiliary actinic or blue fluorescent lighting: lighting that will provide the necessary blue spectrum light needed in photosynthesis of corals and their resident, zooxanthellae.

Ballast: A transformer which changes the voltage from your house outlet to the voltage needed to power different types of lighting such as fluorescents and metal halide bulbs. These are available in several varieties, such as tar, transformer, and electronic. They must be properly matched to the type of bulb you are using.
Basses: 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.
Bio-balls: A filter media used for the colonization of bacteria.
Biological Filtration: These filters make use of bacteria to break down wastes in the water into substances which are less toxic to the inhabitants, in a process known as the nitrogen cycle. 
Biotope: Natural environment of a organism.
Black Water: Water that has a dark cola-like color caused by Humic acids, it has a very low pH and is very soft, common in the Amazon river basin. 
Brackish: Water that part-way between freshwater and marine. A number of species prefer partly-salty water.
Breeding tank: An aquarium set up for the breeding of fish. 
Brine Shrimp: Sometimes sold as sea monkeys, these shrimp grow to about 1/4 inch and are used as a live food for fish. They are easily hatched and their eggs may be stored dry for years. Also called Artemia.
Bubble Filters: These internal filters use a lift tube to draw water through a foam block, as in a sponge filter.
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.
Buffer: A substance which is dissolved in the water to boost the alkalinity and/or adjust the pH. Buffers may be formulated to adjust the pH to a particular value, or to raise the alkalinity without changing the pH.

Calcium: A necessary element used by salt water corals and other organisms for their calcium carbonate skeleton or shell.
Calcium Carbonate: CaC^O3, white chemical compound that is the most common nonsiliceous mineral. It occurs in two crystal forms: calcite, which is hexagonal, and aragonite, which is rhombohedral. Calcium carbonate is largely insoluble in water but is quite soluble in water containing dissolved carbon dioxide, combining with it to form the bicarbonate Ca(HC^O3)2. 
Calcium Chloride: CaCl2. This is a form of calcium that may be added to reef tanks to maintain the calcium level. However, kalkwasser (calcium hydroxide) is preferred, as adding kalkwasser does not upset the alkalinity or ionic balance the way calcium chloride can.
Calcium generator: This device maintains the essential level of calcium (@420 ppm) in a coral reef tank through delivering a Calcium solution to the water: calcium hydroxide, calcium chloride, or calcium oxide.
Calcium Hydroxide: Ca(OH)2. See kalkwasser.
Canister Filter: This filter consists of a canister external to the aquarium which is filled with various media, mechanical or chemical. Hoses run to and from the canister, and an attached pump forces water through the canister. These can be very efficient filters, though they must be taken apart and cleaned regularly.
Carbon: See activated carbon
Carbon dioxide(C⁰²): Important plant nutrient. The higher the dCH the lower the (C⁰²). For most aquarium plants a level of 4-6 dCH is ideal. 
Carbon or Resin filter chamber: Section of the sump chamber that directs the flow of water through the chemical filtering media. 
Carbonate Hardness: The part of the total hardness that is formed by the ions of carbonates(C⁰³) and hydrogen carbonate(HC⁰³). 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. 
Chelators: Synthetic organic acids that enable Iron and other trace elements to be absorbed easily by the plants.
Chemical Filtration: These filters use chemical processes to clean the water. Examples are protein skimmers and any filter containing chemical media such as activated carbon, molecular adsorption pads, or resins.
Chiller: A device which makes aquarium water cooler. They generally cost at least several hundred dollars, and home brew solutions involving small refrigerators are seldom successful.
Chloramine: This substance is sometimes used as a bactericide in municipal water supplies. It it poisonous to fish, but can be removed with special dechlorinating compounds. Unlike chlorine, it will not evaporate from water by itself.
Chlorine: This substance is commonly used to keep bacteria out of municipal water supplies. It is poisonous to fish, but can be removed with special dechlorinating compounds, or by letting a bucket of water sit open for 24 hours. 
Chlorophyll: Is the molecule that absorbs sunlight and uses its energy to synthesis carbohydrates from C^O2 and water. This process is known as photosynthesis and is the basis for sustaining the life processes of all plants. Since animals and humans obtain their food supply by eating plants, photosynthesis can be said to be the source of our life also.
Chlorophyll Absorption: Process of Photo-synthesis - occurs between 420-550 nm. and at 670 nm. Values for different type bulbs: Actinic= 420nm., Vitalite=420-670 nm., Ultralume=550-670 nm. 
C⁰³ and HC⁰³: The ions that form Carbonate Hardness.
Coagulant: A chemical compound used in water clarifiers. It causes fine particles to stick together to be more easily removed by the filter. 
Communities: Different species of fish kept in the same aquarium. 
Contraction: The shedding of the leaves at the onset of the dormant period. 
Controller: A device which measures some parameter of an aquarium, and then switches on and off another device to affect the aquarium. Typical controllers include redox, and pH. 
Convexity: Having the property of curving outward, like the outside of a ball. 
CRI; color rendering index: A number used for rating light bulbs on a scale up to 100, where 100 is equal to sunlight. 
Crushed coral: A Calcareous substrate material with pH buffering abilities, for marine aquaria. 
Cuttings: Detached parts of stem plants: they take root after planting and become new plants. 
Cylinder pump: A type of air pump which can produce great volumes of air, though they are noisier than the more common diaphragm pumps.

dCH: Abbreviation for Carbonate Hardness
Dechlorinating Compounds: A substance used to remove Chlorine and neutralize Chloramines from tap water for use in an aquarium.
Deionization: A process for filtering tap water before it is added to the aquarium. It comes with either separate or mixed-bed resins. The mixed-bed resins are disposable when they are exhausted, whereas separate resins can be recharged, though that requires working with caustic chemicals.
Denitrification: The breakdown of nitrates by anaerobic bacteria, necessary to convert nitrate into nitrogen. 
Denitrification filter: Filter that provides nitrate (N^O3) removal using anaerobic bacterias that separate nitrogen from oxygen. With much attention, the hobbyist may maintain a near zero nitrate level with this living filter. 
Detritus: Organic waste matter that collects on the bottom of fish tanks.
Diaphragm Pump: The most common type of air pump. A great variety of brands and styles are available which produce different amounts of air, with differing amounts of noise. 
Diatom Filter: This purely mechanical filter uses diatomaceous earth to remove very fine particles from the water. They clog quickly and are only used occasionally as water polishers rather than continuously.
Diatoms: Single-celled creatures with hard, silica-based shells. They look like a golden powder coating the tank to the naked eye.
Diatomaceous earth: A filter media made up of skeletons of Diatoms, used in Diatom filters, able to filter particles down to microns in size.
dKH: Abbreviation for Degrees of Carbonate Hardness.
DLS (double-layered spiral): A material made by rolling up a polyester pad and plastic wire mesh. It is used in both biological and mechanical filters.
Dolomite: A limestone gravel with a small pH buffering ability. 
Dosing Pump: A pump which can supply a very slow drip which is used to add trace elements or make up water for evaporation. The most common type is a peristaltic.

Electrical ground probe: Stainless steel or titanium probe that is housed within the tank and connected with a wire to the ground in an electrical outlet or the household plumbing pipes. Used to ensure that the hobbyist and the fish are protected against the threat of shock. 
Endcap: A water resistant socket for fluorescent lamps. 
Etiolation: The formation of weak, spindly foliage deficient in Chlorophyll, usually occurs in light of too low intensity. 
External Filter: Any filter not kept inside the aquarium, but connected with hoses. Canister filters are an example of these.

Filter (or Filtration): 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. 
Filter feeder: A small animal that feeds off tiny food suspended in the water. 
Foam fractionation- See protein skimming. 
5500K: Spectrum temperature of daylight.

General or Total hardness: The sum of carbonate hardness and non-carbonate hardness. Usually expressed in degrees of dKH.
Halogen: Halogen lights have a very yellow light not appropriate for aquarium use. Do not confuse these with metal halide lights. 
Hard water: Water with a high concentration of dissolved salts. 
Heater: A device to warm the aquarium water. They are available as submersible heaters, over-the-side heaters, and under tank coils. 
Hydrogen Sulfide: Hydrogen sulfide gas is also known as “sewer gas” because it is often produced by the decay of waste material. Hydrogen sulfide gas has a strong odor at low levels. At higher levels, your nose can become overwhelmed by the gas and you cannot smell it. At these higher levels, hydrogen sulfide gas can make you sick and even kill you. Hydrometer - A device used to measure salinity of water.

I.D.: Abbreviation for inside diameter, used when measuring tubing dimensions.
Internal filters: Any filter operated inside the aquarium. Under gravel filters and sponge filters are two examples of these. 
Invertebrate: An animal with no backbone. In freshwater aquaria only snails and crayfish/shrimp are generally available. For marine aquaria, many kinds of animals are available. 
Iodine: A trace element necessary to life in very small quantities, but deadly at higher concentrations. Because it is removed by protein skimming, it must be added regularly on skimmed tanks. It is especially needed by crustaceans to successfully molt and soft corals for growth.

Kalkwasser: Literally chalk-water, this is water with calcium hydroxide Ca(OH)2 dissolved in it. Adding kalkwasser is the preferred way to maintain calcium levels in a marine tank with growing corals, clams, and calcareous algae. About 1 teaspoon of Ca(OH)2 powder will dissolve in a gallon of pure water. 
Kelvin: A temperature reading used to rate the color of lite bulbs. 5500 degrees K is equal to sunlight.

Laterite: Substance used in fresh water plant tanks to supply nutrients, either a powder placed under the gravel or chunks mixed in the gravel bed. 
Lift tube: A source of water movement used with under gravel filters and some other filters, such as sponge filters. Large bubbles are released in a tube about 1 inch wide. As they rush upwards, they pull the water in the tube up as well.
Live rock: These are rocks removed from the vicinity of a tropical coral reef with all of the life intact on them. They commonly have algae, sponges, worms, feather dusters, small crustaceans, polyps and urchins on them. Live rocks are an important way to build up a complete and stable ecosystem for a coral reef.
Lumens: A measurement of light intensity. (1 lumen=10.76 lux). 
Lux: The standard for measuring light.

Mechanical filtration: These filters mechanically remove particles from the water. Examples are under gravel filters, canister filters, and wet/dry prefilters.
Media: A form of filtration material.
Metal halide lighting: Metal halide lights are a type of light bulb which burns very white and very bright. They require a special fixture and ballast. They are the closest thing we have to artificial sunlight, and are typically used on reefs and planted tanks. They are very efficient in terms of lumens/watt which provides good surface level intensity, color temperature, and CRI of about 90. Do not confuse these with halogen bulbs, which have a very yellow light not appropriate for aquarium use. 
Molecular adsorption pads: These are polyester pads which have been chemically treated to absorb certain substances from the water. This form of chemical filtration is placed in a canister or power filter. Note that they sometimes will remove good trace elements as well as pollutants.

Nitrification: The process by which ammonia is changed to nitrite, then nitrate, and finally nitrogen gas. See nitrogen cycle. 
Nitrate (N^O3): This is a product in the nitrogen cycle. It is not toxic, though at high levels can cause some distress. In a reef tank it should be kept as low as possible, under 10ppm. Fish only tanks can generally stand 30-40ppm. 
Nitrite (N^O2): This is one of the steps in the nitrogen cycle. It is toxic to most creatures, and should be at un-measurable levels after a tank has cycled.
Nitrogen cycle: The nitrogen cycle describes how organic waste breaks down in the aquarium. Fish waste naturally decompose into ammonia, which is highly toxic. Nitrosomonas bacteria process the ammonia into nitrite, which is also toxic. Nitrobacter bacteria then break down the nitrite into nitrate, which is much less harmful. This is as far as the cycle goes in most tanks, though under the right conditions, the nitrate is further broken down to free nitrogen gas.

Opposing powerhead sumps and surge generators: Device used to change or revolve the flow of water in the aquarium. A varying direction of flow is beneficial in stimulating the growth of anemones, corals, and sponges.
Overflow prefilter: This device removes particles of algae, detritus, and other small particles before the water enters the trickle filter. The floss in the prefilter should be replaced weekly. 
Oxygen or Ozone generator/reactor: A closed filter unit that supersaturates the water with oxygen and/or ozone through slight pressurization.
Ozone: A gas, O3, which is very reactive. It is used as a sterilizing agent to kill bacteria and small organisms in the water. It is used in an ozone reactor or protein skimmer. It is important not to use too much ozone, and to filter ozonated water through carbon before returning it to the tank, as excess ozone can harm fish and other creatures. 
Ozone carbon filter: Filter comprised of carbon removes the ozone from the water. It is important that the carbon filter be placed in the return line of the ozone reactor.
Ozone generator: Device using an electrical spark and air to create the unstable oxygen atom Ozone (O3).
Ozone reactor: Device used to deliver the ozone from the generator into the water in the filter system. Ozone is effective in breaking down most of the complex organic compounds in the system.

Peat: This form of dried moss can be used as a filter material to soften water and make it more acidic.
Peristaltic pump: A dosing pump which works by using rollers to squeeze flexible tubing. 
pH: A measure of the "power of Hydrogen", or how acidic or alkaline a solution is. Some fish are particular and want some specific pH, others will live at a large range of values. Most are sensitive to changes, which should only be made gradually.
pH controller: Device used to control the pH of the aquarium through the addition of carbon dioxide to the system (C^O2). 
Power filter: A filter which hangs on the side of a tank or is submerged in it, containing an internal pump to draw water through. They provide mechanical filtration, and optionally chemical or biological filtration. 
Powerhead: A small submersible pump. They have only one moving part, called the impeller. They are useful to create current within a tank or to drive filters such as under gravel filters, canisters and protein skimmers.
Prefilter: This is a small mechanical filter attached to the input to another filter, usually biological. It is there to make sure that the biofilter does not get clogged with gunk, decreasing its effectiveness.
Protein skimmer: An important part of reef filtration which is essential in the removal of dissolved organic compounds and microscopic particles. This chemical filter, also called a foam fractionator, sends many small bubbles through a column of water to separate dissolved organic compounds from the water. They come in three varieties, venturi, counter-current, and co-current. They are only effective in salt water. They may be placed in the tank, hung on the side, or placed in a sump.
Pump prefilter: A device used to catch stray contaminants from entering the intake of the pump.

Reactor: A device used to add a substance to the aquarium water in a controlled manner. Ozone, kalkwasser, and carbon dioxide are the most common reactors. They are typically a chamber water is pumped through with an injector for the additive.
Redox: Redox, or reduction-oxidation potential, is a measure of how easy it is for organic reactions to take place. This is an indicator of water quality, measured in millivolts with a special probe. Higher values are better. Redox controllers use an ozone reactor to raise the redox potential. 
Reverse osmosis: A process for filtering tap water before it is used in an aquarium. This process generates water slowly and wastes a couple of gallons of water for each gallon of filtered water produced. However it is one of the easiest home methods. 
Reverse under gravel filter: This variant of an under gravel filter runs in the opposite direction, pushing water up through the gravel. It requires water pumps of some sort to run, but needs cleaning less often. 
R/O: See Reverse Osmosis.

Salinity: A measurement of the dissolved salts in the water, measured in parts per thousand (ppt).
Sensing probes: Devices that measure pH, temperature, and redox potential and send this measurement to the respective controllers that may activate the various other devices to maintain the water qualities.
Specific Gravity: Often denoted as "S.G." specific gravity represents a ratio of the weight of a substance to the weight of an equal volume of pure distilled water. The S.G. of pure water is 1.0. Usually, the higher the salinity, the higher the S.G. 
Sponge filter: This filter provides both mechanical and biological filtration. It consists of a large foam rubber (sponge) block connected to a lift tube or small power head. Water is drawn through the sponge, which removes small particles and grows bacteria. 
Strontium: This trace element is necessary for corals, clams, and other creatures with calcareous skeletons to grow. It is most commonly added as strontium chloride SrCl2.
Sump Tank: An additional water reservoir, typically under a tank, to keep equipment out of sight or increase the amount of water in a system.

Trace elements: These are chemicals that are needed in small amounts by the aquarium creatures to survive, like vitamins. They must be replenished with food, water changes, or specific additives.
Trickle filter: This form of a wet/dry filter provides primarily filtration. Water is dripped over some media which is also exposed to the air. This promotes very efficient nitrification. The water may drip from a spray bar or drip plate. The medium may be small pieces of plastic, DLS, or anything else which will support bacteria and not easily clog.

UG or UGF: Abreviation for under gravel filter.
Ultraviolet sterilizer: A device which uses UV light to kill bacteria and other tiny organisms. 
Under gravel filter: This filter provides both mechanical and biological filtration. It consists of a perforated plate placed on the bottom of the aquarium and then covered in gravel. Water is pulled through the gravel, under the plate, and up through lift tubes. 
Venturi: A type of valve which produces bubbles by drawing air into quickly flowing water. It is sometimes used on protein skimmers. 
Wave maker: A device which switches power heads on and off at timed or random intervals, to simulate wave action in an aquarium.
Wet/Dry filter: This is a form of biological filtration which has media exposed to the air to aid in nitrification. Common forms are trickle filters and rotating "paddle wheel" filters.
Zeolite: A naturally occurring ore which will absorb ammonia and soften water. It is only effective in fresh water.