Glossary of Aquarium Terminology

    • abiotic precipitation: the process of an insoluble solid, known as the precipitate (oftentimes calcium carbonate), emerging from a liquid solution (i.e. tank water), usually caused when two soluble salt particles collide and react. The precipitate will fall to the bottom and remain there, or build up inside equipment which can cause problems over time.
    • acid: a chemical or compound that, when added to a solution, will lower the pH if there are no bases to neutralize it. Common acids in aquariums are nutrients (nitrate, phosphate), or other carbon-based molecules found in organic matter. Carbon dioxide reacts with water to form carbonic acid.
    • algae scrubber: a type of filtration device that consists of algae living in a refugium.
    • alkalinity: refers to water's ability to neutralize acid by resisting changes in pH that would make the water more acidic. In the context of aquariums, carbonate hardness (KH) is the main contributor to alkalinity, so much so that any other contributing compounds are usually considered neglible.
    • amino acids: organic compounds essential to all life; fundamental building blocks of proteins.
    • ammonia: a toxic nitrogenous compound released when anything organic breaks down. A large amount of decomposition (e.g. from a corpse or uneaten food) can cause ammonia to spike. Ammonia is lethal and will suffocate fish, coral and invertebrates. Ammonia is constantly being released into the water, so having a healthy biofilter is essential for any aquarium.
    • anoxic: without oxygen. Anoxic zones can occur in thick sand beds or deep crevices in rocks.
    • bacterial supplements: doses of bacterial colonies used to speed up or ensure the growth of a tank’s biofilter during the cycling process. Once bacterial supplements are added to the aquarium, they must be regularly dosed with ammonia by either ghost feeding or adding drops of pure ammonia to the water until animals are introduced to the aquarium.
    • base: a chemical or compoud that, when added to a solution, will raise the pH if there are no acids to neutralize it. Common bases in aquariums are minerals (carbonates, calcium, magnesium).
    • biofilter (or biological filtration): an aquarium’s biofilter consists of bacterial colonies living in the tank’s substrate, filter media, and surfaces. These bacteria are the only means to carry out the nitrogen cycle and convert toxic nitrogenous compounds into less toxic forms (ammonia > nitrite > nitrate). An active biofilter is mandatory for good tank health. See cycling.
    • bioload: the amount (or load) of life (or biological matter) in an aquarium. 
    • buffering capacity: water's ability to maintain steady pH levels. A buffering compound, when part of a solution, will bind to acidic or basic compounds and neutralize them. The buffering capacity refers to the limit that the buffering compounds can neutralize added acids/bases (linked to concentration of the buffering compounds), after which the pH of the water will change. pH buffers are required in aquarium water, because pure water (RO/DI) is neutral, so trace amounts of any introdcued acid or base can swing the pH greatly. There are different buffers to keep water more basic (carbonates and bicarbonates) vs. more acidic (Amazonia soil or humic substances such as peat, coal, or other dead organic matter).
    • calcification: the means by which coral grows, a process of assimilating calcium and other minerals from the water column into the skeletal structure.
    • carbon dioxide (CO2): a waste gas produced by animals during respiration, and a requirement for photosynthesis. Plants require CO2 to grow and will reduce aquarium CO2 levels in water; planted tanks may require that additional CO2 be diffused or otherwise added in order to promote growth. Excess CO2 can asphixiate fish. CO2 molecules are contantly being transferred back and forth between water and air at the surface. Splashing the surface of the water can promote this exhange and help equilize CO2 content of the water to match that of the air. CO2 in water is acidic.
    • coral: marine animals, survive using a symbiotic relationship with algae. The algae lives inside the tissue of the coral. The coral protects the algae and provides it with compounds needed for photosynthesis, and in return the algae provides the coral with beneficial nutrients and amino acids, oxygen, and waste removal.
    • coral bleaching: when a coral expels all the algae within it, turning it completely white. Without the algae, the coral loses its main supply of nutrients.
    • cycling: the process of establishing a biofilter within an aquarium. Once enough bacterial colonies develop to consume and process all ammonia and nitrite compounds as they are produced, the tank is cycled, or established.
    • dechlorination: the process of removing chlorine from tap water. Chlorine is toxic to aquatic life, which is exactly why it is used in our water supply (kills infectious bacteria). Tap water must be treated with dechlorinator before it can be introduced into an aquarium or the inhabitants and biofilter risk death.
    • dilution: the process of reducing the concentration of a chemical or compound by replacing water that does not contain that chemical or compound. This is usually done via water change: removing a certain percentage of the aquarium water and replacing an equal amount of new water. Some math will be necessary if you need to reduce concentrations to specific levels. For example, if nitrate is at 50ppm, a 50% water change would reduce it to the upper limit (25ppm), or an 80% water change would reduce it to a comfortable 10ppm. Be careful: this assumes the new water has 0ppm of nitrate, which is likely. For other parameters like salinity, the water you add might have a concentration less than the tank water but more than zero. Use our water change calculator to help with the math.
    • enzyme: a biological catalyst that triggers or accelerates chemical reactions.
    • established tank: see cycling.
    • ghost feeding: a method for cycling a new aquarium that involves adding food even though there is nothing to eat it. The food will decompose and release ammonia, which is needed to begin the development of a biofilter.
    • glucose: simple sugar produced by plants during photosynthesis and used for respiration.
    • hardness: the level of dissolved salts and minerals in aquarium water. Hardness can be split into general hardness (GH) and carbonate hardness (KH).
    • hardness, carbonate (KH): the concentration of specifically carbonate mineral compounds (carbonates and bicarbonates) within aquarium water. Carbonate compounds are the most effective buffering compounds in aquarium water and are necessary to safeguard against pH fluctuations. Carbonate hardness is the main contributor to alkalinity.
    • hardness, general (GH): the total concentration of all non-carbonate minerals (mostly calcium and magnesium) within aquarium water. These minerals are used in biological processes and are vital to maintain fish health.
    • low-iron: glass with a softer green tint than typical glass, allowing greater light penetration and increased transparency. The result is a high clarity aquarium with a significantly improved viewing experience.
    • necrosis: the death of cells in an organ or tissue.
    • nitrate: a nitrogenous compound converted from nitrite by the biofilter. Although high concentrations are lethal to aquatic animals, plants and algae require nitrates to grow. Excess nitrate will build up and regular water changes are necessary to maintain non-toxic nitrate levels.
    • nitrite: a toxic nitrogenous compound formed after ammonia is processed by an aquarium’s biofilter. Any measurable amount in an aquarium will burn or kill animals. The presence of nitrite in an aquarium is a sign that the biofilter has not been established to the point where it can sustain life.
    • nitrogen: a chemical element present in all living matter, critical for the production of amino acids.
    • nitrogen cycle: cyclical process by which nitrogen atoms are passed between living things through the food chain (organic waste > ammonia > nitrite > nitrate > absorbed by plants > eaten by animals > organic waste). Applies beyond the context of aquariums to all ecosystems.
    • nitrogenous: containing nitrogen. Nitrogenous compounds include ammonia, nitrite, and nitrate.
    • pH: a general environmental indicator that is the cumulative result of many different chemicals and compounds (especially alkalinity / KH). It is a measure of the acidity or basicity in water. While fish are able to tolerate steady pH levels within a narrow range, they are most intolerant to rapid changes in pH, even if within the range. Because water enters fish down to their very cells through osmosis, a change in pH changes the pH of their blood too. Regulating their internal pH takes time and energy, so pH should be maintained constant to a 1/10 precision (e.g. constantly 8.2, not swinging between 8.1 and 8.3). All aquarium plants and animals have a certain range of pH which they can tolerate before suffering ill effects. While choosing different plants and animals for an aquarium, make sure that all species can thrive in the same pH. Reef aquariums should be slightly basic (pH > 7) and planted aquariums should be slightly acidic (pH < 7). Research the specific pH required for the species you wish to keep.
    • pH buffer: see buffering capacity.
    • photosynthesis: the process by which plants use sunlight to produce food (glucose, etc.) from carbon dioxide and water. Oxygen is a waste product.
    • refugium: a refuge for organisms to live in safety, in a separate reservoir away from the display tank, usually in the sump.
    • RO/DI: “Reverse-Osmosis” and “De-Ionization” are sequential filtration methods to bring water to a very high level of purity. Void of all impurities, RO/DI water is actually too pure for use in aquariums, and correct amounts of minerals and salts should added back into the water before using in a water change. However, RO/DI is appropriate for topping up water lost to evaporation, since the minerals and salts from the evaporated water remain inside the aquarium.
    • water change: necessary to remove excess buildup of nitrates and other waste, and the best  way to maintain desired mineral concentration and salinity. Minerals are constantly being depleted from aquarium water, so replenishment through weekly water changes is mandatory for a successful aquarium. Typically performed by removing a percentage of aquarium water and re-adding the same volume of prepared “change” water. Use our water change calculator to calculate the percentage of water you should change based on the concentration of a certain chemical or compound.