M - Aquarium Dictionary

Updated August 12, 2019
Author: Mike - FishLore Admin
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Aquarium Fish Definition and Glossary

Magnesium :
element Mg, atomic number 12, is the third most abundant element in natural sea water in concentrations of 1200 - 1300 ppm. For our purposes, it is used up by coralline algae and other algaes during photosynthesis within a saltwater aquarium. Get a magnesium test kit before dosing magnesium in your tank. Mg is closely tied to the calcium and alkalinity levels in sea water as well. Not having enough magnesium could pose problems when trying to maintain calcium and alkalinity levels.

Mantle :
refers to the top, colorful, fleshy part of the tridacnid clam species, such as the Crocea Clam. The clam mantle contains symbiotic zooxanthellae that helps provide nutrition to the clam.

Maracyn :
an aquarium fish medication used to treat fungal infections. More info here:

Mariculture :
is the aquaculturing, farming or raising of fish or invertebrate species using water from the ocean. For example, tridacnid clams are often cultured in canals or raceways that are connected to the ocean to provide a continuous influx of clean saltwater.

Marine Biologist :
Marine Biology is the study of marine (saltwater) organisms. This includes all the animals, fish, plants, invertebrates, corals, etc. that live in the water. A marine biologist is the one who studies these organisms. Considered a dream job for many saltwater hobbyists.

Matrix :
an aquarium product made by Seachem that is highly porous media used to remove ammonia, nitrite and nitrate from freshwater, reef and saltwater tanks. See:
Seachem Matrix
Seachem Matrix

Mbuna :
is a common name for African cichlids from Lake Malawi that can be aggressive and territorial. They are a rock-dwelling species of cichlids.

Mechanical Filter :
an aquarium filter that performs the function of removing the larger, suspended particles from the tank water. If the mechanical filter is not maintained regularly they can become a source for nitrate buildup.

Media Bag :
a fine mesh filter bag used to hold aquarium filter media like activated carbon, ceramic bio rings, phosphate removers and others. See:
Media Bag
Media Bag

Melafix :
an aquarium fish medicine that is used to heal bacterial infections, repair damaged fins, ulcers and open wounds.

Metal Halide :
a very high intensity aquarium light (HID) that is used for growing coral in saltwater reef tanks and they are also sometimes used in freshwater planted aquariums. They are about the brightest and most intense light that is currently practical for aquarium use. Metal Halide lamps need special fixtures and ballasts and put out significant heat. Fans and possibly an aquarium chiller may be needed for keeping the tank temperature within acceptable levels. They come in various wattages, anywhere from 125 watts through 1000 watts.

Methylene Blue :
a frequently used fish medication used to treat fungal infections in fish. It can be used as an alternative to malachite green. Methylene Blue is considered safe to use on fish eggs to prevent fungal infections. Some hobbyists also report success using it on external parasites such as ich, chilodonella and costia.
Methylene Blue
Methylene Blue

Metronidazole :
a fish medication used to treat protozoan and anaerobic bacterial diseases of fish (Cryptocaryon, Hexamita, Ichthyophthirius). Seachem metroplex is often used. More below:

mg/L :
abbreviation for millegrams per liter and a unit of measurement that is approximately equivalent to PPM.

Molybdenum :
a trace element in natural saltwater that is used by the symbiotic algae (zooxanthellae) in corals. Also see the Saltwater Aquarium Supplements article.

Moneywort :
an aquarium plant, Bacopa monnieri, is moderately hardy and grows up to 12 inches in height. See:
Moneywort Plant

Monte Carlo :
an aquarium plant, Micranthemum sp., is a foreground or mid ground plant that grows very dense. See:
Monte Carlo Plant
Monte Carlo

Montipora Capricornis :
see Montipora Capricornis.

Montipora Digitata :
see Montipora Digitata.

Montipora Spongodes :
see Montipora Spongodes.

Mopani :
is a type of driftwood hobbyists use in their aquariums. For an example, see:

Mouth Brooder :
fish that hold eggs and fry in their mouths. Many cichlids and the Banggai Cardinal fish (saltwater fish) are mouth brooders.

abbreviation for Multiple Tank Syndrome. This syndrome usually afflicts those aquarists that have achieved success with keeping fish. They soon want "just one more tank" in order to keep a different or bigger species. They may not know it at the time, but they will soon get a third tank. The cycle continues until you run out of space or money. This syndrome spreads quickly and takes tremendous willpower to keep in check. There is no known cure at this time. Preliminary studies have shown that posting on the FishLore forum may make symptoms worse most likely due to the fish keeping enablers found there. Proceed with caution. Laughing

MTS could also be in reference to Malaysian Trumpet Snail. You have to use the context in which the abbreviation is used to determine which one it is referring to. See:
Malaysian Trumpet Snail
Malaysian Snails

Mutualism :
a form of symbiosis in which both organisms derive some benefit from the association with each other.

Mysis Shrimp :
a small shrimp like crustacean that is used as a fish food, especially for finicky eaters such as the Seahorse. More info:
Mysis Shrimp
Mysis Shrimp