Freshwater Dolphin Fish 101: Care, Size, Diet & Tank Mates

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The Freshwater Dolphin Fish are rare species in the aquarium trade. Their name, Dolphin Fish, originates from their bottle-like snout, making them similar in appearance to the oceanic bottlenose dolphin.

Unfortunately, there’s a lot of misinformation being passed around online regarding these creatures due to their interesting look.

For starters, contrary to what some may believe, these fish are not actually dolphins. They are a type of freshwater fish closely related to ray-finned fishes.

Moreover, Freshwater Dolphin Fish is not a specific species, and the common name is specifically given to certain Mormyrids that don’t have extended mouthparts.

It’s always a good idea to know what you’re doing before you buy a pet, so this guide gives you all the information you need to know about Freshwater Dolphin Fish. From a basic description to housing and feeding, you’ll find out how to keep your fish healthy and happy.

Let’s get started!

Species Summary

The Mormyridae is a diverse family with almost 221 recognized species, is also known as freshwater elephantfish, and originates from the waters of Africa. These elephantfish come with an extended “elephant-like” snout that is used for mud-sifting and waiting to ambush their prey.

The shape and structure of mouthparts are one of the main ways to tell apart different members of Mormyridae.

Species with long, sharp, and tubular snouts are known as the popular “elephant-nosed fish.” The most well-known species is Peters’s elephant-nose fish (Gnathonemus petersii). Most Mormyrids are sold as this species at the local fish store. Be aware this species is a far smaller species in the genus. 

As we mentioned before, more than one species under the common name Freshwater Dolphin Fish. The most popular ones in the aquarium trade are:

  • Mormyrus Tapirus
  • Mormyrus longirostris (Eastern bottlenose mormyrid)
  • Mormyrus Lacerda (Western bottlenose mormyrid)
  • Mormyrus Kannume (Elephant-snout fish)
  • Mormyrus Rume
  • Marcusenius macrolepidotus (Bulldog)

These species are medium-sized fish with a shorter and more bottle-like snout.


Freshwater Dolphin Fish

The most distinct feature of Freshwater Dolphin Fish is their short and extended snout. In addition, they have large brain sizes due to their enlarged cerebellum, which is also why they are incredibly personable and intelligent.

Another interesting adaptation is the auditory vesicle located in their inner ears, which can be used for communication and self-defense.

These species have a torpedo-shaped body with a brown, grey, or black coloration. The underside is usually lighter in color.


The average lifespan of the freshwater dolphin fish is 5 – 8 years, but some have been known to live up to 10 years with great habitat and top-notch water quality in captivity— the number of two years of age dominates the population.

Freshwater Dolphin Fish Size

The average Freshwater Dolphin Fish size depends on the particular species. Here are the average sizes of these most popular species:

SpeciesMax Size
Mormyrus Tapirus 17 inches (43 cm)
Mormyrus longirostris (Eastern bottlenose mormyrid)30 inches (75 cm)
Mormyrus Lacerda (Western bottlenose mormyrid)19.6 inches (50 cm)
Mormyrus Kannume (Elephant-snout fish) 23.6 inches (60 cm)
Mormyrus Rume11.8 inches (30 cm)
Marcusenius macrolepidotus (Bulldog)11.8 inches (30 cm)
Date from fishbase

Care And Tank Set-Up

Although the members are different in size, they all come from the same natural habitats in Africa. Most of them come from rivers with stagnant or slow-moving water, and they prefer muddy areas and soft bottoms.

Many sellers describe these fish as shy and sensitive. Unfortunately, this is another piece of misinformation spread throughout the community and social media. It’s just the other way around, and these dolphin Mormyrid fish are very aggressive and hardy species. 

Due to their size and temperament, it’s not recommended for beginners to start with these fish. They need a lot of space and care, which can be too much for a beginner to handle. 

Freshwater Dolphin Fish Tank Size

These species vary in full-growth size and purchase size, but they all need a large tank. The recommended minimum tank size for a single Freshwater Dolphin Fish is 125 gallons. If you plan on housing multiple juveniles at a decent purchase size, you will need an even larger tank.

But no matter the purchase size of your Freshwater Dolphin Fish, they will grow big and always need plenty of room to swim and explore. So if you’re thinking of adding a Freshwater Dolphin Fish to your home, make sure you have the space to accommodate them first.

Water Parameters

Water parameters are not the most critical aspect of mature Freshwater Dolphin Fish care; they are really hardy fish that can tolerate a flexible range of water parameters. However, young fish under 6 inches can be very sensitive to water conditions; slight changes can cause a lot of stress.

As an owner, your job is to make sure the parameters are as stable and consistent as possible and provide them with the best habitat you can.

The ideal Freshwater Dolphin Fish tank should have the following water parameters:

  • Water temperature: 77°F to 82°F
  • pH level: 6.0 – 7.5
  • Water hardness: 0-10 KH
  • Ammonia levels: 0 ppm
  • Nitrate: <20 ppm

It‘s highly recommended to purchase 6 inches or larger size specimens whenever possible because they are much more likely to acclimate and survive in your home aquarium.

Because juveniles require a lot of stability in water conditions, it’s essential to do regular water tests and maintain high water quality. An accurate aquarium testing kit is necessary for all Freshwater Dolphin Fish caretakers. This will allow you to make adjustments accordingly.

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Just like other electrical species, these fish are scaleless. They are subject to chemical changes and metal content in the water. Any items that contain copper, salt, iron, and other chemical and metal ingredients might be fatal to your Freshwater Dolphin Fish.

Substrate and Décor 

A soft sandy substrate with no sharp edges decors is critical that you’ll pay the most attention to. Freshwater dolphin fish are middle to bottom dwelling fish species that spend most of their time burrowing in the substrate for small invertebrates and tasty food.

To make sure your Freshwater Dolphin Fish are as safe as possible, avoid any sharp-edged or coarse decors that will damage their mouthparts and prevent them from feeding naturally.

Smooth rocks, driftwood, and low lighting live plants are all great additions that will help create a natural and stress-free environment. It’s best to choose the tough and tall plants as they might be uprooted. Don’t plant too heavily, which will make it hard for the fish to swim freely.

As far as I know, the Mormyrus Kannume (Elephant-snout fish) is a solitary, nocturnal species. Thus, dim or “spot” lighting is required to make it feel secure.


Freshwater dolphin fish are some of the most intelligent fish in the aquarium world. Typically, large species are just for show, but the Mormyrid Dolphin fish have been known to follow their owners and learn tricks with time and patience.

I first noticed their intelligence when I saw a video on YouTube of one solving a puzzle. The fish was trying to figure out how to get food that was just out of reach. It was amazing to watch.

After that, I started paying more attention to these fish, and I found they could play with toys, just like what you see at the National Aquarium. They are truly remarkable creatures.

Food & Diet

Unlike the farm-bred species, such as Oscars, you may have a problem getting these wild caught species to eat commercial pellets when you first bring them home.

The best way to start is to mimic their natural diet as much as possible. In the wild, they mostly eat worms of all sorts. If you’re frustrated getting your new Freshwater Dolphin fish to eat man-made food, hikari bloodworms are the way.

When they get used to the taste and nursed back to health, you can start mixing in other food items such as brine shrimp or frozen foods with the bloodworms.

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Adult Freshwater Dolphin Fish will readily accept most meats. Like all fish, they can be trained to eat dried pellets eventually, but it may take a long time and patience to get used to it.

Freshwater Dolphin Fish Tank Mates

Freshwater Dolphin Fish with Bichir

Because they’re so large and very aggressive, finding good tank mates is tricky. They are not the best community fish and can be kept with other large, aggressive fish that can take care of themselves.

Like other aggressive species, like Betta fish or cichlids, it’s best kept singly as a show fish. They are extremely aggressive towards their own species and will fight to the death if given a chance. If you plan to keep more than one, you’ll need a large tank with lots of hiding places.

Here are some potential species that can be kept with Freshwater Dolphin Fish:

To add, they should not be kept or mixed with other electric fish. This is because the electrical currents of other fish may interfere with theirs.


Freshwater Dolphin Fish have been popular in the aquarium trade for many years, but unfortunately, there is no report of Freshwater Dolphin Fish breeding in captivity. The majority of Freshwater Dolphin Fish in trade are caught in the wild.

Final Thoughts

Now, you have a better understanding of the Freshwater Dolphin fish and how to care for them. These fish are not for everyone, but if you have the time, patience, and space, they can be a great addition to your aquarium.

Freshwater Dolphin fish are hard to obtain at your LFS, so finding a reputable online dealer is your best bet. There are many good places to start your search.

Due to their solitary nature and scarcity on the market, much of their behavior remains a mystery. If you have experience or suggestions on Freshwater Dolphins’ care, please share in the comments below.

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Jeff Colt

Jeff Colt

Hello, I'm Jeff- an aquarium enthusiast with over 25 years of experience caring for a wide array of tropical fish, including koi, goldfish bettas, cichlids and more! For me: Aquariums are like jello - there's always room for more!

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