Get in the know, all sorts of glossary terms used by ichthyologists and aquarists alike!
This aquarium glossary comes in real handy for both beginners and advanced hobbyists.
Have you ever been stumped by the terms used in the aquatic world, like dorsal fin, barbel, or how about gonopodium? That’s where this dictionary of scientific terms, related to freshwater aquatic and marine animals, comes in very handy.
There are lots of unique words used to describe parts of fish, plants or other water critters. These terms are not only unusual, but actually quite interesting. And the more you read, the more questions that will come up. But beware, with the list of aquarium glossary terms, you’ll find answers and then you’ll start thinking like an aquatic expert!
A – C
amyloodinium– Amyloodinium ocellateum is commonly called Oodinium, Marine Velvet, or Saltwater Ick. Possible signs of the disease are cloudy eyes, gasping for breath, listlessness, and white spots. Positive signs of the disease are gold or brown spots, rough skin, and rubbing against rocks, etc. Treatment can be done by a freshwater dip and copper (as long as inverts are not in the tank).
anthostele – The lower part of the polyp, often stiffened, into which the distal portion of the polyp, the anthocodia (which includes the mouth and the eight tenacles) is withdrawn. The calyx.
ascidians – Also known as sea squirts. Filter feeding animals found exclusively in marine environments that come in a variety of shapes and sizes. Due to their appearance they are frequently confused with sponges or even rocks. Most are sessile, meaning they don’t move, and are attached to the substrate, but a few deep water species can move and are predatory.
aufwuchs – the German term “aufwuchs” refers to microscopic food consisting of small animals, algae and other plant matter that grown on and encrusts hard surfaces, such as rocks or other substrate. Fish that graze on this type of food are called Limnivores.
- Sessile – means the organism is attached to the substrate.
- Pelagic- refers to living in the water above the bottom. Pelagic organisms usually have some ability to move around.
- Brackish water should have enough salt added to reach a specific gravity in the range of 1.002 to 1.008. Since brackish water is generally a mixture of freshwater and saltwater, a high quality saltwater mix works best but pure rock salt will work in a pinch. NEVER USE IODIZED SALT!
- A hydrometer is needed to measure salinity but be sure that the one used will measure the necessary range. Most hydrometers found in aquarium stores are made for measuring pure saltwater so they will not measure the lower salinity needed for brackish. A couple direct reading of specific gravity and ppt. that will work for these lower levels are: Instant Ocean Salinity Hydrometer manufactured by Marineland Labs, and SeaTest Full Range Specific Gravity Meter manufactured by Aquarium Systems.
Some fish live in salt water but are spawned in brackish or fresh water and vice versa. There are several brackish species available in the aquarium hobby, see Freshwater Fish for descriptions.
byssus gland– The structure in clams that produces fibrous threads (byssus) that attach the clam to substrate. Sometimes permanent although more usually temporary attachment of tough organic threads secreted from a gland in the foot of the clam.
calcyes – plural for calyx. See anthostele.
coelenterate – an aquatic animal of the Phylum Coelenterata which is characterized by a central mouth usually surrounded by tentacles bearing stinging cells, and no anus; includes sea anemones, corals, and jellyfishes.
coenenchyme – a stiff gelatinous matrix found on certain soft corals that anchors and supports the polyps, and may be embedded with sclerites or other particulate matter. The tissue of a zoanthid that surrounds the polyps, consists of mesoglea and may have sand imbedded in it.
comensal, comensalism – one of several types of symbiotic relationships between the individuals of two (or more) different species In a comensal relationship one species benefits while the other does not (see symbiosis).
cryptocaryon – Cryptocaryon irritans is a parasitic infection where white spots appear on the body and fins. Fish will scratch themselves against rocks and breathing may become rapid if gills are affected. Treatment can be done by copper or other anti-parasite remedies, but this is incompatible with inverts. Cleaner shrimps and wrasses will remove the parasites, but may not keep up with a major infestation. Cryptocaryon is often referred to as the marine equivalent of the freshwater white spot disease, Ichthyophthirius, or Ick.
cyanobacteria – Cyanobacteria is commonly referred to as red slime algae by hobbyists although it is not really an algae. It is a bacteria. Poor water quality with excessive nutrients are the usual causes. To combat, do frequent water changes, siphon out detritus, and use a good protein skimmer.
D – H
detritus – grayish piles of organic compounds that accumulate in the aquarium. Commonly will contain fish wastes, fragments of rock, leftover food, among other things. Usually detritus will accumulate in low water flow areas, sumps, etc.
gorgonian – a tropical or subtropical octocoral with upright branchy plant-like or fan-like growths and a skeleton made of a horny organic material. For example, the Sea Fans (Scientific names: Gorgonia ventalina, G. flabellum, G. mariae, Pacifigorgia spp.)
head and lateral line erosion – also known as lateral line erosion, hole-in-head disease, and lateral line disease. A fish with this condition will develop holes in its’ head and sometimes along its’ lateral line. The main cause is nutritional deficiency, especially vitamin C. Stress and poor water quality also play a role. Untreated cases will cause disfiguring or death. To combat and cure, ensure good water quality and provide vitamin enriched foods, especially vitamin C.
hermaphrodite – refers to both male and female in the same organism. This occurs either at the same time (synchronous hermaphrodite) or at different times (successive hermaphrodite). When the female form occurs first, this is referred to as protogynous hermaphroditism, otherwise protandrous hermaphroditism.
hydrometer – an instrument used to determine the specific gravity of a fluid. Hobbyist grade hydrometers are temperature corrected to read the specific gravity at around 77F (25C) because specific gravity is temperature dependent.
I – O
ichthyophthirius, Ick: see cryptocaryon.
kalkwasser – German word meaning ‘calcium water’, kalkwasser is a mixture of calcium hydroxide in water. The ph is very high (around 12.0) and it is used as makeup water to replace calcium used by hard corals and clams to build calcerous skeletons.
lateral line – The lateral line is a line of perforated scales along the flanks of a fish which lead to a pressure-sensitive nervous system. This enables the fish to detect vibrations in the surrounding water caused by other fish and their own reflected vibrations against obstacles.
limnivore – limnivores are also known as “mud-eaters” or “bio-film grazers”. Liminores are fish that eat algae, microorganisms and other things it can find at the bottom of its habitat. This is what is meant by the German term “aufwuchs” that has gained popular use.near the shore.
mantle – large, pigmented fleshy portion of tridacnid clams that is exposed to the light by gaping of the shell valves. Also called siphonal tissue. Also, the coral tissue in fleshy polyps (e.g. Catalaphyllia).
mimicry – when an animal ‘mimics’, or ‘copies’ the appearance of another animal in order to gain an advantage, like camouflage or a better defense. A good example is the marine fish, Mimic tang.
mutualism – one of several types of symbiotic relationships between the individuals of two (or more) different species. In a mutualistic relationship both species benefit, see symbiosis.
omnivore – animals who eat both meat and vegetables like marine angelfish.
P – R
parasitism – one of several types of symbiotic relationships between the individuals of two (or more) different species In a parasitic relationship one species benefits, the other is harmed (see symbiosis).
pelagic – refers to living in the water of the ocean above the bottom. Pelagic organisms have the ability to swim around or move in some fashion. “Pelagic” is also used to refer (usually) to eggs that are basically at the mercy of the ocean currents. Benthos and benthic refers to living on or under substrate at the bottom of the ocean. Sessile means the organism is attached to the substrate.
phytoplankton – microscopic free-floating aquatic plants, mainly algae. It lives suspended in bodies of water and drifts about. See plankton.
plankton – plankton are the drifters of the sea. Although they may have some form of locomotion they are mostly carried by water currents. Plankton is divided into macroplankton (jellyfish, sargassum weed) and microplankton, organisms that can only be seen by a microscope. The microplankton is divided into zooplankton, tiny marine animals, and phytoplankton, or plants. Most fish start their lives as small animals in the plankton.
red slime – see cyanobacteria.
S – Z
sessile – sessile means the organism is attached to the substrate at the bottom of the ocean and therefore cannot move around. Pelagic refers to living in the water of the ocean above the bottom. Pelagic organisms have the ability to move around. Benthos and benthic refers to living near or under substrate at the bottom of the ocean.
specific gravity – as a hobbyist definition, specific gravity is the amount of salt in the water. See the hydrometer definition above for more information. Specific Gravity of seawater ranges from 1.022 to 1.030.
sweeper tentacle/polyp – a coral tentacle or polyp that has an increased number of nematocysts and elongates in order to ‘sting’ neighboring corals and sessile invertebrates. See the Frogspawn coral, Euphyllia divisa for a picture of sweeper tentacles.
symbiosis – a close ecological relationship between the individuals of two (or more) different species. Sometimes a symbiotic relationship benefits both species, sometimes one species benefits at the other’s expense, and in other cases neither species benefits.
symbiotic – a relationship where two or more different kinds of animals live together and both benefit in some way from the other’s company. The most famous example is the clownfish and the anemone.
wood eater – wood eaters are fish, like some types of plecostumus, that can digest wood. They use “friendly bacteria” to break down the wood to simpler forms of carbohydrates that are then digested by the fish.
zooplankton – small, usually microscopic animals; includes tiny waterborne crustaceans and fish larvae, also includes corals, rotifers, sea anemones, and jellyfish. – See plankton.
zooxanthellae algae – pronounced ‘zo-zan-thel-ee’, zooxanthellae algae are tiny plants called dinoflagellates (single-celled microscopic organisms which belong to the Protista kingdom) that live symbiotically with corals, tridacnid clams, and some sponges. The algae provides food for the host and in return gets the nitrogen, phosphorous, and carbon dioxide it needs to grow. The scientific name is Symbiodinium spp.
Featured Image Credit: Daniel Corneschi, Unsplash