15 Aquarium Fish That Start With M (With Photos)

The letter M might contain one of the fish you’re looking for! You might find it slightly challenging to think of any tropical fish species that start with the letter M, and that’s for a reason. While many fish start with M, they’re some of the lesser-known species available in the hobby. That isn’t to say they can’t make a great new addition to a freshwater or saltwater aquarium, though!

Here are some of the few Fish That Start With M and others you may not have known existed!

Fish That Start With M

Here is a list of the most popular fish beginning with M along with a few others that you may not know!

1. Molly Fish

• Scientific Name: Poecilia sphenops, P. latipinna, P. velifera, etc.
• Fish Family: Poeciliidae
• Water Type: Freshwater, brackish water, saltwater
• Temperament: Peaceful, but active
• Care Level: Moderate
• Size Range: 3-7 inches
• Special Features: Various colors; elongated fins

Mollies are probably the first freshwater fish that comes to mind that starts with the letter M. But did you know that these fish can live in freshwater, saltwater, and brackish water conditions? This means that they can be kept in salinities between 0 to 1.025.

Molly fish come in all shapes and sizes. In fact, many species of molly fall under the Poecilia genus. Apart from coming in almost every color imaginable, there are several distinct species of molly available:

• Giant sailfin molly (Poecilia velifera) – These mollies have exceptionally long dorsal and caudal fins. They often have a natural speckled pattern with some splashes of orange and blue. Giant sailfins are also one of the biggest species of molly available.
• Balloon molly (Poecilia latipinna hybrid) – A selectively bred species with an overly inflated belly. Balloon mollies come in almost all colors.
• Lyretail molly (Poecilia latipinna hybrid) – Another selectively bred molly, lyretails have decorative tail fins. They also come in the most popular colors.

Mollies are easy to find and easy to keep. They need at least a 15 gallon tank, though their active behaviors are better seen in a 20 gallon setup. Though some hobbyists have success keeping these fish alone, it is often recommended to keep them in small groups or larger schools.

2. Malawi Golden Cichlid

• Scientific Name: Melanochromis auratus
• Fish Family: Cichlidae
• Water Type: Freshwater
• Temperament: Aggressive
• Care Level: Moderate to expert
• Size Range: 5 inches
• Special Features: Bright colors; highly aggressive

Many popular species of African cichlids come from Lake Malawi, though the Malawi golden cichlid, or auratus cichlid, isn’t usually on that list. This is because the Malawi golden cichlid is one of the most aggressive mbuna and is usually only kept in 55 gallon or more fish tanks by themselves.

That’s right. These fish are so aggressive that they are best kept alone.

This extreme aggression is especially troubling during breeding periods, making pairing these fish with other mbuna species or each other nearly impossible. Because of this, this cichlid species is difficult to keep, though well worth it for their bright yellow and black striped pattern.

3. Midas Cichlid

• Scientific Name: Amphilophus citrinellus
• Fish Family: Cichlidae
• Water Type: Freshwater
• Temperament: Semi-aggressive
• Care Level: Moderate
• Size Range: 10-14 inches
• Special Features: Nuchal hump

A much more approachable species of freshwater cichlid to keep is the Midas cichlid. Though larger than most other species of Central American cichlid, the Midas cichlid has nearly twice the personality.

These orangey-yellow freshwater fish require at least a 75 gallon aquarium, with more space allowing for additional species similar in size and temperament. It’s also important to note that male Midas cichlids have especially pronounced nuchal humps. The water line should be lowered a few inches from the top of the tank cover to prevent injury.

These fish should not be confused with the red devil cichlid (Amphilophus labiatus).

4. Moonlight Gourami

• Scientific Name: Trichopodus microlepis
• Fish Family: Osphronemidae
• Water Type: Freshwater
• Temperament: Peaceful
• Care Level: Moderate
• Size Range: 4-6 inches
• Special Features: Silver shine

The moonlight gourami, also known as the moonbean gourami, is a less commonly known fish species that starts with M. These fish are a reflective silver which can shine blue or green depending on the lighting and angle.

This is one of the larger aquarium gourami species available, but they are fully compatible with each other and community tank species. Alone, they can be kept in a 20 gallon aquarium. With more fish, it’s recommended to have at least a 40 gallon or more aquarium. Moonlight gouramis also have longer feelers than other gouramis, so it’s best to avoid keeping them with fin nippers and powerful filtration.

5. Marbled Bichir

• Scientific Name: Polypterus polli
• Fish Family: Polypteridae
• Water Type: Freshwater
• Temperament: Semi-aggressive
• Care Level: Moderate
• Size Range: 11-13 inches
• Special Features: Upper jaw group

Bichir are great freshwater fish if you have room for them (video from Imperial Tropicals). The marbled bichir is one of the smaller species of bichir available, staying around about a foot long at full length, but still requires at least 125 gallons or more. This, in addition to their carnivorous diet, makes these fish best kept in a species-only or predatory tank.

The marbled bichir originates from shallow regions of the Congo River in Africa. They are members of the upper jaw group, meaning that their upper jaw is longer than their lower jaw. While these fish are generally easy to keep, a tight-fitting aquarium lid should be used at all times.

6. Mickey Mouse Platy

• Scientific Name: Xiphophorus maculatus
• Fish Family: Poeciliidae
• Water Type: Freshwater
• Temperament: Peaceful
• Care Level: Easy
• Size Range: 2-3 inches
• Special Features: Mickey Mouse patterning

The Mickey Mouse platy (video source) is a selectively-bred variety of platy that features a fun Mickey Mouse design. These fish have a large black spot at the base of their tails, with two smaller black dots on either side of the tail. Together, this makes up Mickey’s head and ears.

Fun and easy to keep, the Mickey Mouse platy is a good freshwater fish for hobbyists looking for more intentional patterns in their aquarium. As with almost all livebearers, these platies will easily breed, which could possibly lead to overpopulation. While a 10 gallon tank size is recommended, they will often out-populate an aquarium that size.

7. Marbled Hatchetfish

• Scientific Name: Carnegiella strigata
• Fish Family: Gasteropelecidae
• Water Type: Freshwater
• Temperament: Peaceful, but timid
• Care Level: Moderate
• Size Range: 1-2 inches
• Special Features: Natural coloring

The marbled hatchetfish is a great fish species for hobbyists looking to create a natural tank inspired by South America. Unlike their shiny distant relatives, the silver hatchetfish (Gasteropelecus sternicla), the marbled hatchetfish is perfectly camouflaged with tan and dark brown striping and feels most comfortable in a heavily planted aquarium.

While active swimmers at the top of the aquarium, these small fish need plenty of places to hide and swim, so a 20 gallon aquarium is recommended for a group of 6 or more. As they are timid, a tight-fitting aquarium hood must also be used.

8. Mosaic Gourami

• Scientific Name: Trichopodus leerii
• Fish Family: Osphronemidae
• Water Type: Freshwater
• Temperament: Peaceful
• Care Level: Moderate
• Size Range: 4-5 inches
• Special Features: Irridescent spots

More commonly known as the pearl gourami, the mosaic gourami is named after the many small iridescent spots that cover its body. These moderately sized fish stay toward the aquarium’s upper portions.

Though not overly active, these fish enjoy having a lot of space to explore and need at least a 30 or 40 gallon setup. Mosaic gourami also enjoy heavily planted aquariums with calmer tank mates.

9. Moss Barb

• Scientific Name: Puntius tetrazona
• Fish Family: Cyprinidae
• Water Type: Freshwater
• Temperament: Semi-aggressive
• Care Level: Easy
• Size Range: 2-3 inches
• Special Features: Varying shades of green

For one reason or another, these fish known from its common name tiger barbs have lost their popularity over the years. In some cases, temperaments can greatly vary between individuals which can make grouping and pairing with other tank mates difficult. However, the moss barb offers fluorescent shades of light to dark green that can’t be found in other species.

That being said, variation in temperaments can still be a problem with moss barbs. They are also active fish that need to be kept in schools in a 30 or 40 gallon aquarium.

10. Magnificent Rasbora

• Scientific Name: Rasbora borapetensis
• Fish Family: Cyprinidae
• Water Type: Freshwater
• Temperament: Peaceful
• Care Level: Easy
• Size Range: 2-3 inches
• Special Features: Neon yellow line; tight schooling

More commonly known as the red-tailed rasbora, the magnificent rasbora is a fascinating fish that might take some time to take on its true colors. These fish are initially plain-looking, especially if they’re washed out due to stress from temporary housing and poor diet. At full brilliance, the magnificent rasbora takes on a solid silver appearance with a bright neon midlateral line, underlined by a thicker black line. There is a splash of reddish-orange at the base of the tail.

The magnificent rasbora (video source) is relatively easy to care for and recommended for beginner hobbyists. They need a school of at least 6 or more and will demonstrate tight schooling behaviors. Their minimum tank size recommended is 10 gallons.

11. Minnows

• Fish Superfamily: Cyprinoidea
• Water Type: Freshwater
• Temperament: Peaceful, usually active
• Care Level: Easy
• Size Range: 1-3 inches
• Special Features: Effective mosquito control; adaptable to varying water temperatures

Have you ever seen tiny fish at the surface of freshwater rivers or streams? More than likely, these were a type of freshwater minnow. The term minnow is a very general name for many species, some of which have been brought into the aquarium and pond hobbies.

Some of the most well-known species of minnow are:

• Zebra danios (Danio rerio)
• White cloud mountain minnows (Tanichthys albonubes)
• Rosy red minnows (Pimephales promelas)

Most species of minnow prefer cooler temperatures but can be slowly acclimated to more tropical settings. In the wild, minnows are an important part of the food chain and can help moderate pest populations by eating mosquito larvae and adult insects.

12. Marlboro Discus

• Scientific Name: Symphysodon spp.
• Fish Family: Cichlidae
• Water Type: Freshwater
• Temperament: Peaceful
• Care Level: Moderate to expert
• Size Range: 6-10 inches
• Special Features: Bright red, black, and yellowish-white coloration

The Marlboro discus is probably one of the most desirable freshwater fish beginning with M. This is a variety of discus with a bright red body, yellowish-white face, and contrasting black tail.

As a species of discus, these fish should only be kept by experienced hobbyists in 55 gallon or more aquariums. They can be difficult to feed, require a certain diet, and need excellent water quality. So much so that some hobbyists find themselves having to perform large water changes daily. On the other hand, some discus keepers find that they are much more hardy fish than we give them credit for.

13. Marine Betta

• Scientific Name: Calloplesiops altivelis
• Fish Family: Plesiopidae
• Water Type: Saltwater
• Temperament: Peaceful, but predatory
• Care Level: Moderate
• Size Range: 8-10 inches
• Special Features: Contrasting spots; nocturnal

The marine betta is not related to the freshwater Betta splendens. Instead, this is a saltwater fish that thrives in rocky reefs. This fish is a predator by nature that waits for small fish and invertebrates to pass by. The eye spot on the tail is used to confuse fish as it looks like the face of a moray eel.

While the marine betta can’t be kept with small fish or invertebrates, they do well in a full reef setup of at least 55 gallons or more with larger species. It should be noted that marine bettas are nocturnal fish, so they might not be the most present fish in the aquarium display.

14. Marine Angelfish

• Fish Family: Pomacanthidae
• Water Type: Saltwater
• Temperament: Semi-aggressive; not reef-safe
• Care Level: Moderate
• Size Range: 8-12 inches on average
• Special Features: Bright colors; large bodies

Marine angelfish are some of the most coveted saltwater fish in all of the aquarium hobby. These are large, colorful fish that swim in and around reef structures throughout the Atlantic and Pacific Oceans. There are many species of angelfish available, with some being small enough to keep in nano setups under 40 gallons.

Here are some of the most well-known species of marine angelfish available:

• Coral beauty angelfish (Centropyge bispinosa)
• Flame angelfish (Centropyge loricula)
• Emperor angelfish (Pomacanthus imperator)
• Bicolor angelfish (Centropyge bicolor)
• Koran angelfish (Pomacanthus semicirculatus)

Despite the varying species, each angel behaves in a similar way. These are relatively active fish that will weave in and out of the rockwork looking for something to eat. Though some species might be labeled as being reef-friendly, we don’t recommend putting any species of angelfish in along with corals that you wouldn’t want to be eaten as there is always a risk.

15. Moray Eel

• Fish Family: Muraenidae
• Water Type: Saltwater
• Temperament: Semi-aggressive to aggressive
• Care Level: Moderate
• Size Range: 3-6 feet on average
• Special Features: Pharyngeal teeth

If you have a large predatory saltwater fish tank, then the only thing that might be missing from your display is an eel. Moray eels are some of the most well-known saltwater fish beginning with M, though most people wouldn’t consider them to be fish.

Believe it or not, there are a handful of moray eels that can be purchased for the aquarium. Of course, these are large fish that need large tanks, though some of the smaller species can comfortably be kept in a 55 gallon setup.

Here are some of the most popular types of moray eel available:

• Snowflake eel (Echidna nebulosa)
• Tessalata eel (Gymnothorax favagineus)
• Zebra Moray (Gymnomuraena zebra)
• Blue ribbon eel (Rhinomuraena quaesita)

Creatures That Can’t Be Kept In Aquariums

While many aquarium fish start with M, some species are too big or aggressive to be kept in captivity. Here are some of those fish:

1. Mustache Triggerfish (Balistoides viridescens). Also known as the giant triggerfish, the mustache trigger grows to be 30 inches at adult size. In addition to its size, these fish are naturally aggressive and will chase away and attack any fish that enters its territory. The mustache triggerfish has a specialized diet of corals and various invertebrates that help trim its hard beak. All of these factors make this fish difficult to keep in the home aquarium.
2. Mako Shark (Isurus oxyrinchus). The mako shark is an apex predator of tropical and subtropical waters. This type of mackerel shark can grow to be 13 feet long and can swim at speeds greater than 30 mph! Due to their high activity, intense carnivore tendencies, and migratory patterns, the mako shark is rarely seen even in the largest public aquariums.
3. Marbled Swamp Eel (Synbranchus marmoratus). The marbled swamp eel is a very long eel, reaching lengths of 60 inches. These fish have pretty specialized habitats and are one of the few fish that can be found ahead of waterfalls. There, they eat tadpoles as well as other fish and amphibians. Like other eels, marbled swamp eels can travel on land.
4. Mexican Golden Trout (Oncorhynchus chrysogaster). The Mexican golden trout is small enough to be kept in the aquarium, only growing to about 8 or 10 inches. However, these fish originate from very specific freshwater streams in Mexico. There, they are an important commercial fishery species for local people. Luckily, they have been named as a vulnerable species and efforts are being made to protect their limited natural range.
5. Mud Catfish (Pylodictis olivaris). Also known as the flathead catfish, mud catfish live in freshwater and brackish water conditions. These fish grow over 60 inches and feed on a variety of prey, including other fish, invertebrates, and insects. Mud catfish are regularly fished and eaten. Public aquariums with large tanks often keep them on display.
6. Manta Ray (Manta sp.). Some of the most elegant fish in all of the world’s oceans, the term manta ray refers to a scientific group of marine rays. These rays can be 30 feet in length and rely on zooplankton, krill, and other microscopic organisms!

Other fish that can’t be kept in the home aquarium are mahi mahi (Coryphaena hippurus), also known as dolphinfish, mangrove red snapper (Lutjanus argentimaculatus), and murray cod (Maccullochella peelii).

Other Honorable Mentions

Here are fish that we run out of space for that you may have heard about

• Millions fish (AKA Guppies)
• Malawi Blue Dolphin
• Mail Cheeked Fish
• Bait Fish
• Mexican Tetra
• Megamouth Shark
• Man Of War Fish
• Midshipman Fish

Other Lists

Looking for other fish that start with other letters of the alphabet? Check out the other posts below:

• Fish that start with S
• Fish that start with P
• Start that start with B

FAQ

Conclusion

Numerous species begin with the letter M, but not every fish is right for the aquarium setting. Luckily, some of the most well-known M fish can be kept in the community tank or reef tank. Before deciding which M fish is right for your tank, make sure to research the species in full!

• About the Author
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Mark Valderrama

I’m thrilled that you found Aquarium Store Depot! Here you’ll find information on fish, aquariums, and all things aquatics related. I’m a hobbyist (being doing this since I was 11) and here to help other hobbyists thrive with their aquariums! I adhere to a high quality Editorial Process and Review products with real life field usage and practical analysis.

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