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.
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.
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.
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.
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.
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.
Memorable rearspined fin prickleback
Kasatkia memorabilis
Kasatkia memorabilis is a tiny, eel-shaped marine prickleback from the Sea of Japan area that spends its life down on the bottom in nearshore water. Its whole vibe is "hide in cracks and hug the rocks," so if you ever did keep one, you would treat it more like a coldwater tidepool fish than a tropical reef fish.
Menderes garra
Garra menderesensis
A small-bodied cyprinid endemic to Lake Işıklı and the Büyük Menderes River system (Turkey). Described in 2015 (originally as Hemigrammocapoeta menderesensis) and currently treated as Garra menderesensis. Aquarium husbandry information appears scarce; avoid extrapolating care requirements from unrelated Garra species without species-specific sources.
Mexican stargazer
Dactyloscopus metoecus
This is a teeny sand-stargazer that spends its time buried with just the eyes poking out, waiting to ambush tiny prey. Super cool little "sand-periscope" behavior, but its whole lifestyle is basically built around being in clean marine sand, so it is not a typical aquarium fish at all.
Midas blenny
Ecsenius midas
Midas blennies are those weirdly "blenny-but-also-open-water" fish that zip around the tank like a tiny golden torpedo, then duck into a hole like nothing happened. They'll even color-shift and loosely school with anthias in the wild, which is honestly one of the coolest behaviors you'll see in a reef fish.
Milkspotted puffer
Chelonodontops patoca
This is that chunky, curious puffer with the milky white spots and big "what are you doing?" eyes that follows you around the glass like a little water puppy. It's a super fun fish to watch-always cruising, inspecting everything, and begging for food-but it's also one of those puffers that really needs the right setup as it grows (and it grows a lot).
Milkspotted puffer
Chelonodon patoca
This is the big milk-spotted brackish puffer that cruises estuaries and mangroves and sometimes wanders a little way into fresh water. It gets chunky (over a foot) with those clean white spots, and it has that classic puffer personality - curious, food-motivated, and sometimes a bit too interested in other fish's fins. Long-term it really does best as a brackish-to-marine fish with hard, alkaline water and lots of crunchy shell-on foods to keep the beak worn down.
Min County plateau loach
Triplophysa minxianensis
This is a coldwater, fast-river Triplophysa from Gansu, China - a little bottom loach built for current, with that classic 'stone loach' shape and a life spent hugging the substrate. Its wild range seems pretty localized (Taohe River and upper Weihe), and in the hobby its care gets tricky mostly because it really wants cool, super-oxygenated water and a clean, river-style setup.
Minerim banjo catfish
Bunocephalus minerim
This is a tiny little banjo catfish from Brazil that basically lives the stealth life - it melts into leaf litter and sand and you can go days thinking it vanished. Super chill fish, but it is one of those bottom hiders you feed with intention (sinking foods after lights-out), and it really appreciates a soft substrate to burrow into.