Glossary of Aquarium Terms

This glossary of aquarium terms contains definitions for some of the most common words used in the hobby.


Acclimate - The process in which one will allow for a inhabitant to move from one water source to another (such as moving from the pet store's tank to your own aquarium).

Acidic - Relates to the pH scale in where anything that is measured below a pH of 7.0 is considered an acid (or acidic).

Aeration - Refers to increasing the amount of air that is passed through the water in an aquarium (also known as creating surface agitation to do so).

Aerobic - Requires the presence of oxygen in order to survive.

Ahermatypic - Relates to corals that do not have zooxanthellae and are generally not reef building coral.

Algae - A simple nonflowering aquatic plant of a large group that contains chlorophyll but lacks true stems, roots, leaves, and vascular tissue. Some algae can be beneficial while others can be labeled as a nuisance/issue.

Alkaline - Relates to the pH scale in where anything that is equal to or above a pH of 7.0 is considered a base (or basic/alkaline).

Alkalinity - The capacity of something to resist a downward change in pH (normally referred to as carbonate hardness).

Ammonia - NH3 is a toxic chemical byproduct produced during the breakdown of proteins in uneaten fish food, decaying waste, or excreted by aquatic animals inside of the aquarium.

Anaerobic - Refers to something that can survive in conditions without any oxygen.

Aragonite - A calcium based material that is used in substrates of aquariums.

Asexual - An organism that has no sexual organs, and therefore is neither male or female.

Autotrophic - An organism that is capable of synthesizing (creating) its own food from inorganic substances.


Bacteria - Referring to microorganisms that are found, which some can be beneficial (ex; Nitrosamines and Nitrobacteria in breaking down waste) or harmful (those that act as pathogens attacking fish with infections or diseases).

Benthic - The bottom of a body of water, such as the seafloor or bottom of a lake where flora and fauna are found.

Bioball(s) - A biological media that is used in filters. Normally are made of plastic, in a spherical shape, and have designs on the outside to attach growth of beneficial bacteria.

Biological Filtration - The use of filter media to grow colonies of aerobic and anaerobic bacteria to remove ammonia and nitrite from the water.

Bioluminescent - Microbes and animals that are able to produce their own light.

Biomass - Refers to the total mass of living matter within a specified area (normally referred to as bioload).

Biomechanical - The use of filter media that contains both mechanical and biological filtration inside of one unit.

Bleaching - The process in which zooxanthellae expel themselves from corals causing a lack of pigmentation in the given coral.

Blushing - A pink or reddish appearance normally associated to on a fish.

Brackish - Water that has a slight salt content with a specific gravity between 1.006-1.015. Found naturally where rivers meet the ocean.

Buffering - The capability of something to resist changes in pH.






GH - General Hardness is a measurement of total calcium and magnesium.





KH - dKH is a measurement of bicarbonates and carbonates and is also known as total alkalinity or acid-neutralizing capacity.


LFS - Local Fish Store (or Shop)



Nitrate - A toxic byproduct of the nitrogen cycle that is the least toxic nitrogen byproduct often used by live plants.

Nitrite - A toxic byproduct of the nitrogen cycle that is often broken down and used by plants in a planted aquarium or can be removed with water changes.



pH - Measurement of relative alkalinity or acidity within a specific type of liquid. A pH reading of 7.0 is considered neutral, higher than 7.0 being a base/alkaline and readings lower than 7.0 are acidic.

PPM - Abbreviation for Parts Per Million that is used as a a measurement of a particular element commonly used in test kits.



RO - Reserve Osmosis is water that has been fully stripped of all minerals and elements, to only contain pure H2O. It is commonly used to replace evaporated water.