Fish That Start With M
Browse all aquarium fish species with common names beginning with "M". Each profile includes care requirements, water parameters, tank size recommendations, and compatibility information for freshwater, marine, and brackish species.
The letter 'M' features a diverse array of aquarium species, ranging from popular community favorites to unique exotic fish. Notable entries include the vibrant Boeseman's rainbowfish (Melanotaenia boesemani) and the charming Ram cichlid (Mikrogeophagus ramirezi). Whether you are interested in schooling fish like the Serpae Tetra (Megalamphodus eques) or the intriguing Fire eel (Mastacembelus erythrotaenia), this section showcases species that can enhance both beginner and advanced aquariums.
Mabahiss lightfish
Vinciguerria mabahiss
Vinciguerria mabahiss is a tiny deepwater lightfish from the Red Sea that uses rows of photophores (light organs) for counter-illumination - basically a living stealth mode in the midwater dark. Its whole lifestyle is mesopelagic (open-water, deep), so its "care" is really more science-lab territory than home aquarium stuff.
Macedonia shad
Alosa macedonica
Landlocked shad endemic to northern Greece; formerly occurred in Lakes Volvi and Koronia but now restricted to Lake Volvi. Spawning occurs in summer (July–August) and begins around 19–20 °C.
Machete
Elops affinis
Elops affinis is a sleek, super-silver coastal predator (a ladyfish) that cruises surf zones, bays, and estuaries in schools and will happily push into brackish lagoons. Its life cycle is pretty cool - spawning happens offshore, and the clear, ribbon-like larvae drift in toward the coast before they grow into those fast, fork-tailed little missiles.
Macra headstander
Laemolyta macra
Laemolyta macra is a small South American anostomid (headstander family). Some references have treated it historically as Laemolyta garmani macra, but at least some major databases list Laemolyta macra as a valid species rather than a synonym of Laemolyta garmani.
Maculate panray
Zanobatus maculatus
Zanobatus maculatus is a small coastal panray from the Gulf of Guinea with a blotchy, spotted top-side pattern and a bottom that can look pale/creamy to orange-brown. It is a demersal (bottom-living) marine ray that hangs out on sandy (and often muddy) shallows, and it is mostly a bycatch species in local fisheries rather than something you will realistically see in the aquarium trade.
Maltzan's goby
Wheelerigobius maltzani
This is a tiny West African coastal goby that lives right down on the bottom in warm, shallow inshore water. Its big appeal is the "little predator" vibe - it perches, scoots, and hugs structure like a classic goby, but its real-world habitat is marine shoreline rather than a typical freshwater community setup.
Mandarinfish
Synchiropus splendidus
This is the classic mandarin dragonet-the little reef crawler that looks like someone hand-painted neon blue and orange squiggles onto a fish. It spends basically all day pecking at live rock for tiny pods, and at dusk you can sometimes catch the pair-spawning "rise" if you keep a bonded male/female. Absolutely reef-safe, but it's one of those fish that does amazing only when the tank is truly mature and full of microfauna.
Mandeville's loach catfish
Zaireichthys mandevillei
This is a tiny little Congo River loach catfish that stays about an inch long, with a bold dark collar right behind the head and a speckly pattern. Its basically built for life in moving water - it likes to tuck into sand and squeeze around rocks - so its a super cool "micro-catfish" for a river-style setup if you can actually source one.
Mandi
Rhamdioglanis frenatus
Rhamdioglanis frenatus is a freshwater heptapterid catfish endemic to Brazil's Atlantic Forest coastal drainages (SE Atlantic). It reaches about 22 cm total length and is primarily carnivorous; in aquaria it is expected to appreciate ample shelter and floor space, though detailed species-specific husbandry data is scarce.
Mangrove whipray
Urogymnus granulatus
This is a large, heavy-bodied whipray with a dark disc sprinkled with small pale spots and a distinctive white tail beyond the sting. It uses shallow inshore habitats including mangroves and estuaries (juveniles often in brackish areas). Juveniles have been documented actively producing clicking sounds during aggregations/defensive interactions.
Manyara tilapia
Oreochromis amphimelas
Manyara tilapia is a Tanzanian Rift Valley tilapia endemic to closed-basin saline/alkaline (soda) lakes such as Lakes Manyara, Eyasi, Kitangiri and Singida. Territorial males can show dark/black underside and fins with pinkish-red on the flank and caudal fin, and the species is a mouthbrooder (reported primarily maternal).
Marlier's julie
Julidochromis marlieri
Julidochromis marlieri is a rock-dwelling Lake Tanganyika cichlid with that awesome checkerboard pattern that looks like it was painted on. Give it a maze of rocks and tight caves and you will get to watch real cave-spawning, territory-guarding cichlid behavior up close. They can be absolute jerks to other Julidochromis, so plan the tank around that and they are a blast.
Marquesas dwarf flounder
Engyprosopon marquisense
This is a tiny deepwater lefteye flounder from the Marquesas Islands - one of those little sand-hugging ambush fish that looks like a leaf until it moves. Super cool biologically, but honestly not a realistic home-aquarium fish since it comes from 108-408 m depths and there is basically no established hobby care info for the species.
Marshall's grenadier
Coryphaenoides marshalli
This is a deep-sea grenadier (rattail) from the Gulf of Guinea - think big head, huge eyes for the dark, and that classic long tapering tail. It lives way down on the slope, so it's not an aquarium fish in any realistic sense, but it's a really neat example of how fish are built for cold, high-pressure life.
Mary River cod
Maccullochella mariensis
Mary River cod is a big, thick-bodied Australian freshwater predator with that awesome dark mottled patterning and white-edged fins. Its basically a sit-and-wait ambush fish that likes deep pools and heavy cover (snags, undercut banks), and it gets way too large for normal home aquariums.
Masked greenling
Hexagrammos octogrammus
Masked greenling is a cold-water North Pacific greenling that hangs around shallow rocky areas and kelp, cruising the bottom and picking off crustaceans. One of the coolest quirks is the family trick of eye/cornea color shifting in different light, which is just wild to see in person. This is not a typical home-aquarium fish - it gets fairly big and wants chilly, super-oxygenated marine water.
Masked julie
Julidochromis transcriptus
This is a little Lake Tanganyika rock-dweller with bold black-and-white striping and that cool dark "masked" face. Give it a pile of rocks and tight caves and it will cruise around like it owns the place, especially once it pairs up. Small fish, big attitude - but in a manageable, "fun to watch" way if you plan the tank around territories.
Matthes' synodontis
Synodontis matthesi
Synodontis matthesi is a chunky little African squeaker catfish from Tanzania's Rufiji River system that tops out around 12 inches. Expect a shy, cave-loving daytime hider that comes alive at feeding time, and like most Synodontis it can wedge itself into the tightest spot you thought was impossible.
McCosker's coralbrotula
Ogilbia mccoskeri
This is a tiny, super-secretive little reef brotula from the SW Caribbean that spends its life tucked into coral rubble and crevices. It is a bottom-hugging carnivore that picks off small mobile crustaceans, and you will mostly see it at dusk or when food hits the water. Cool fish, but it is absolutely not a typical aquarium species, so most "care" info out there is guesswork or confused with McCosker's flasher wrasse (totally different fish).
Medem's brycon
Brycon medemi
Brycon medemi is a small-ish Brycon from Colombia's Atrato River basin. It is basically a streamlined, open-water characin with that classic Brycon look (built to cruise and grab food), but the hobby reality is: there is almost no solid aquarium-specific info published for this exact species, so you treat it like a fast, jumpy, river fish and give it space and clean water.
Megasema eartheater
Geophagus megasema
Geophagus megasema is one of those classic sand-sifting eartheaters that spends all day taking mouthfuls of sand, filtering out snacks, then "spitting" the clean sand back out. Give it a soft sandy bottom and roomy floor space and it really comes alive, plus that big side spot is a dead giveaway when you see one in person.
Mekong sheatfish
Kryptopterus paraschilbeides
Kryptopterus paraschilbeides is a small Mekong River sheatfish that does the whole sleek, no-dorsal-fin Kryptopterus look, but its body is more "normal catfish" than the super see-through glass catfish you usually see in shops. In the wild it moves with the flood cycle - heading into flooded forest at high water, then back to the main river seasonally - which is a pretty cool bit of behavior for a little catfish.
Mekran ponyfish
Deveximentum mekranense
This is a small ponyfish from the Gulf of Oman off Iran, and like other ponyfishes its whole vibe is being a little bottom-hugging, silvery coastal fish. It is a pretty recent species description (2021), and its natural range is very localized, so you are not going to see it come through the aquarium trade in any normal way. If you ever did encounter one, you would treat it like a delicate wild marine schooling fish rather than a typical hardy "saltwater beginner" fish.
Meleiro livebearer
Jenynsia sanctaecatarinae
This is a little onesided livebearer from southern Brazil that stays pretty small, with males topping out around 3.7 cm and females around 4.2 cm. In a planted stream-style tank they are always cruising and picking at tiny foods, and like other Jenynsia they have that cool livebearer biology (no eggs to babysit). I'd treat them like a slightly feisty nano livebearer and give them space and a group so nobody gets singled out.