Dragon fish are exciting because they hint at a world far beneath the surface of the oceans that few people will ever get to visit. Each one is a creature that looks like life from another planet, with jet black skin, light-emitting organs, and mouths full of vicious teeth.
But there are more to dragonfish than deep-sea predators and prey. There are also fish closer to our own surface world of light and freshwater habitats!
Let’s take a look at the many different kinds of dragonfish out there and what makes them so interesting!
Understanding Deep-Sea Dragonfish
Deep-sea dragonfish are found in temperate and tropical waters all around the world. They are even found in the depths of the Arctic and Antarctic Oceans, alongside many other species of fish. How can they survive even in the frozen habitat of the polar seas?
Water temperatures in temperate and tropical waters actually don’t vary as much as you would think once you start getting into the truly deep ocean regions. This is because heat is circulated all over the world by deep undersea currents. Since they don’t need light and can easily find warmth, dragonfish species can live anywhere in the world so long as there is prey to find!
While they are unique and truly draconic-looking deep-sea creatures, you are unlikely to ever see a deep-sea dragonfish in a pet store or even a public aquarium. They need to live in the specialized environment of the deep sea, where the water pressure, cold, and silence are all immense. Things like constant light and fluctuating temperatures would stress them severely.
In fact, many deep-sea fish explode when brought to the surface since their bodies are pressurized to fight against the force of all of that water crushing against them. So it is best to leave dragonfish to the depths of the Pacific Ocean, where they belong!
- Scientific Name: order Stomiiformes
- Origin: deep oceanic waters around the world
- Aquarium Size: N/A
- Length: 1 to 20 inches
- Temperament: unknown
- Ease of Care: N/A
Are Black Dragon Fish Poisonous?
The most iconic species of deep-sea dragonfish is probably the black dragonfish (Idiacanthus atlanticus). They live mostly in the southern hemisphere in depths down to 2 kilometers, where sunlight can’t penetrate the depth of the ocean.
Like many deep-sea fish, black dragonfish have light-producing photophore cells running along the length of their bodies. But unlike many bioluminescent species of animal, they don’t use theirs to attract prey. In fact, black dragonfish produce light that is barely visible and closer to infrared light (heat). Instead, they use their light like flashlights to help them see in the dark!
So far as we know, black dragonfish aren’t poisonous. They do have huge, fang-like teeth and a snake-like appearance so you’d be forgiven for thinking they are like snakes with a venomous bite! But they use their teeth purely for catching other fish, shrimp, and anything else that wanders by in the deep sea.
The fry of these deep-sea dragonfish are also extremely unusual. Their small eyes are set on stalks that are one-half the length of their entire body! They look more like sea slugs than fish!
If you are interested in learning more about these unusual fish, this article from the Australian Museum is very educational!
What Do Black Dragon Fish Eat?
Notice all of the sharp teeth in its mouth? As predators, black dragonfish feed on any creature that is small enough to be overpowered. However, they can often eat animals that are much larger than you’d think!
To attract prey many species of fish in the deep oceans use light to lure them in. Many dragonfish also do this – but in the case of the black dragonfish, only the female has a photophore on a long chin barbel that she uses like a dangling lure of her own light.
Males not only don’t have a light-producing barbel – they don’t even have a digestive system! The sole purpose of the male black dragonfish is to find a female to mate with.
Many species of dragonfish can unhinge their jaws a full 100º to swallow animals close to their own size. But what if their prey emits light of its own? An even bigger predator might be attracted to the now bloated and easy-to-capture deep-sea dragonfish.
Fortunately, their stomachs are coated in black pigments, blocking any light from their meals from shining forth, which could attract unwanted attention.
What Other Dragonfish Species are there?
Since the deep-sea dragonfish is only found in waters too dark and far to ever keep in an aquarium, we won’t be able to ever see one at home. But are they the only dragonfish out there? As it turns out, there are a few that are much closer to the surface. In fact, there are even a few aquarium dragonfish to consider if you are in love with how these animals look!
Blue Glaucus Dragon Fish
Blue glaucus, also known as the sea swallow, sea moth, blue dragon, or blue angel, is one of the most otherworldly animals you will ever see! They also aren’t dragons – nor are they even fishes!
The Blue glaucus is actually a species of pelagic, free-swimming nudibranch (sea slug)! Instead of crawling along the bottom of the ocean the blue dragon instead seeks out siphonophores, which are gelatinous, venomous sea creatures similar to jellyfish.
One of their favorite meals is the highly dangerous Portuguese man o war, a colonial organism that has a vicious sting. Interestingly, the blue glaucus has the ability to not only ignore the stings of its meal but reuse them for its own defense!
See those blue tendrils that line its body? The blue angel packs the nematocysts (defensive stinging cells) of the Portuguese man o war into them, where they can be triggered if a fish (or person) comes into contact with them. It is a highly effective defense that’s perfect for a sea swallow that has no shell and nowhere to hide in the open ocean!
Dragon Koi Fish
There are many types of koi fish out there, including classic varieties like the Kohaku and Taisho Sanke. But did you know that there are also dragon koi fish as well?
You also see these sold as butterfly koi; their long, trailing fins remind viewers of both dragons and butterflies. So you can choose whichever common name you prefer!
That said, dragon koi fish are neither predators nor nectar feeders. Instead, they consume algae, worms, soft plants, and other organic material in their pond habitat, just like any other koi.
Dragon koi fishes can also come in any color variety because the fin form is what determines whether or not they can be called dragons or not! They are one of the easier freshwater dragon fish to find as a result!
Dragon Violet Goby
Of the many fishes listed here, these gobies are definitely fish that look like a dragon! In fact, they have the same prehistoric look as many creatures that spend their life at depth. However, you won’t find the Violet Goby in the open ocean. They are brackish water fish, meaning they spend most of their time in the transition between freshwater rivers and oceans.
The Dragon Goby can live in pure saltwater as well but they prefer brackish water to freshwater that has been lightly salted.
While the Dragon Goby is not really a rare fish they aren’t super common in pet stores. Since they do need some salt they tend to do poorly in captivity if aquarists that buy them are not aware of this fact.
But given a touch of aquarium salt or true brackish water for optimal health, the Dragon Goby can be a hardy and long-lived aquarium resident! These dragonfish look aggressive but they are actually passive and peaceful, feeding on small fish and invertebrates like worms and brine shrimp!
Arowana Dragon Fish
The last dragonfish to learn about today is the freshwater arowana! They are commonly called dragon fish, especially in Asia as they remind viewers of iconic East Asian mythological creatures.
For starters, these are impressively large, predatory fish with a large head and mouth with whisker-like barbels. An Asian Arowana can easily grow to be around 3 feet long once fully grown. They are a common addition to Asian banks, restaurants, and other establishments because they are traditional symbols of good fortune.
Even the skin of an arowana is reminiscent of dragons! The large, armor-like scales are very distinctive, as are the trailing tips to their fins. And their skin and scale color have a metallic quality to it that furthers their draconic appearance.
That said, these are dragonfish that you should take some time to consider before buying. Arowanas need to feed several times per day and they eat a lot! They also need to have a tank that is hundreds of gallons in volume, with plenty of swimming area since arowanas rarely rest.
In Conclusion
We’ve learned about the lives of some of the most diverse and interesting dragonfish you will ever see! Many of them are found in the deep ocean, where you might never find one, even in a tank at a public aquarium. But hopefully, this article gives you a taste of the dragonfish possibilities hidden in the ocean and rivers of the world!
Other Frequently Asked Questions about Dragon Fish
Black dragonfish look like something from a nightmare or another planet entirely. But they are very real and one of the least weird things you will ever see if you could descend down into the depths where they are found.
Deep-sea dragonfish live in an environment that’s far too extreme for us to keep them alive for long. But any of the freshwater dragon fish pet choices detailed here make fine additions to your tank. So long as you can provide them with the water parameters and aquarium size that they need, that is!
As far as we know, no one has tried eating a deep-sea dragonfish before. So we don’t know if they are edible or not. Freshwater dragonfish like the arowana may be edible but they are so valuable that no one would want to! A high-quality arowana can cost hundreds of thousands of dollars!
