Hatchetfish; an appropriately named little tropical fish thanks to the shape of its body. As it turns out that hatchet shape is very functional and something that makes the hatchetfish very special!
What are hatchetfish and how can we care for them in home aquariums?
Let’s find out together!
Getting to Know the Hatchetfish
Freshwater hatchetfish are unique fish that are closely related to tetras, silver dollars, piranhas, and pacus. These fish are all members of the order Characiformes and are found almost exclusively in South America, where they have adapted to fill nearly every niche a fish could live in.
Hatchetfish are specialized in an interesting way; these fish can fly, which complicates caring for them. They are peaceful to the point of being shy and skittish as well, so they are only suitable for tanks full of other quiet community fish.
Hatchetfish are a little more sensitive to dissolved waste products as well and don’t tolerate poor water conditions. So only keep them in mature, cycled tanks that have no detectable ammonia or other pollutants.
Scientific Name: family Gasteropelecidae
Origin: South America
Length: 1 to 3 inches
Aquarium Size: 10 to 40 gallons
Temperament: Peaceful; Schooling; Shy
Ease of Care: Intermediate
Marbled Hatchetfish and Related Species
There are quite a few species of hatchetfish that enter the trade occasionally. Only half a dozen of them are seen at all and of those, only 3 are really common.
Marbled Hatchetfish
And of the 3 we most commonly see the Marbled Hatchetfish is the most popular! It’s easy to see why: they have a complex, attractive pattern of chocolate brown markings over their silver base that’s quite beautiful. When kept in subdued lighting and well planted tanks the chocolate tones intensify and a faint green sheen covers the fish.
Marbled Hatchetfish are a smaller species as well, making them well suited to aquariums for beginners because some of the other kinds are many times larger!
- Scientific Name: Carnegiella strigata
- Origin: Bolivia, Peru, Colombia, Brazil
- Length: 1 to 1.5 inches
Silver Hatchetfish
The Silver Hatchetfish is a larger species, growing up to 2 inches long. They are plainer in appearance but still attractive; their vibrant silver scales remind you of Silver Dollars, distant cousins of theirs. Black speckles and gold lines run along the side of the fish and the back becomes darker the higher up you get.
- Scientific Name: Gasteropelecus levis
- Origin: Amazon Basin
- Length: 2 inches
Giant Hatchetfish
The Giant Hatchetfish really could have been called the Silver Hatchetfish as it lacks any of the black speckling of its smaller cousin. Giant Hatchetfish are truly silver, fading into gold as you move towards the back of the fish. It is a lovely effect and makes them easy to identify when young. Reaching up to 3 inches in length Giant Hatchetfish have the largest space requirements for Hatchetfish – only keep them in aquariums 40 gallons or larger.
- Scientific Name: Thoracocharax securis
- Origin: Amazon Basin
- Length: 2.5 to 3 inches
Pygmy Hatchetfish and Other Types of Hatchetfish
A few other species seen occasionally include the Pygmy Hatchetfish (Carnegiella myersi), which only grows just past an inch in length and the Blackwing Hatchetfish (Carnegiella marthae). The rest are very rare imports that you’ll be lucky to ever find in the hobby but often show up online through specialty distributors!
Freshwater Hatchetfish Flying
Believe it or not hatchetfish flying is not only real but something you need to plan for when buying them as pets. Hatchetfish are one of the few fish that actually can fly! Flying fish as we usually think of them are completely unrelated saltwater fish.
And they don’t fly; they rocket out of the water at high speeds and then glide. They hold their pectoral fins out and wiggle, which simulates a flap for added lift. But they get by mostly on gliding.
You can see how flying fish glide here: https://www.youtube.com/watch?v=bk7McNUjWgw
Freshwater hatchetfish, on the other hand, actually can fly in a true fashion! In fact, their flight specialization is the reason why they have such a strange shaped body. They have enlarged pectoral muscles in the shape of a keel, just like a bird! They literally beat their fin-wings to stay aloft longer and gain more elevation!
Here is a brief video that shows freshwater hatchetfish flying out of the water in response to a predator’s attack. While they don’t really fly horizontally they do create actual lift when jumping to gain much more height than you’d expect from such tiny fish!
Freshwater Hatchetfish Care
The hatchetfish is not as popular as Neon Tetras and other Characiform fish but they deserve to be! That’s why I’ll be breaking down how to succeed with these unique flying fish in the guide below!
Aquariums for Common Hatchetfish
Hatchetfish size means that they can be kept in aquariums well suited to a beginner’s budget. 15 to 20 gallons is a good start if keeping Silver Hatchetfish. And a small school of Marbled or Pygmy Hatchetfish can live in a 10-gallon tank so long as they have very few tank mates.
The only hatchetfish size you need to be worried about is when keeping Giant Hatchetfish. Since they grow up to 3 inches long and are schooling fish they should be kept in aquariums no smaller than 40 gallons. They are surface dwellers but are quite active so they need plenty of space.
Remember how I mentioned that these fish can literally fly? Sooner or later your freshwater hatchetfish will try and gain some elevation. Perhaps they are startled by you moving too quickly around their tank or abruptly turning on the lights. Or an aggressive tank mate decides to chase one.
When a hatchetfish takes a leap, ideally you will have a secure lid in place to prevent them from landing on the floor. Beware of any sizable holes in your setup. Remember that these fish have very good vision and have nothing better to do than stare at the surface of the water. If they see a hole where light is entering they can easily aim for it and make a leap, which may end up with them on the floor.
Hatchetfish and Aquatic Plants
Freshwater hatchetfish get along really well with aquarium plants. In fact, I would almost say they are mandatory for them. Plants provide nearby cover so these surface dwelling fish don’t feel quite so exposed, thinking a bird or net is going to descend at any moment.
Floating plants like red root floaters, duckweed, and salvia all give ample cover to these fish. What’s more, they also shade the lower regions, preventing algae from taking hold and soaking up nutrients that algae would normally use!
You can also keep hatchetfish in aquascapes with traditional rooted plants; they will get along splendidly with them and won’t eat or pick at your plants. Aquarium plants even provide them with a place for hatchet fish reproduction to occur, which we will get into later.
Hatchetfish Freshwater Conditions
Hatchetfish are not the most difficult fish to keep but neither are they especially easy. The majority are actually wild-caught and shipped from Brazil and other Amazonian countries so they are used to pristine, soft, acidic water conditions.
The hard, alkaline water found in the aquarium hobby is stressful for them and a major cause of diminished longevity and death over time. The pH for hatchetfish should never go much past neutral and if you can bring it close to blackwater conditions (pH 4.5-5.5) that’s even better!
Removing water hardness is not easy but additives can help counteract the buffering minerals from your tap. Refilling the tank with reverse osmosis or distilled water when doing aquarium maintenance also helps keep the pH close to neutral.
Plant sources of tannins and humic acids also help buffer the water towards neutrality. A few of these include Indian almond leaves and driftwood!
Ammonia, nitrite, and nitrate should always be as close to 0 ppm as possible. Since they are mostly wild caught fish, hatchetfish have very little tolerance for high levels of these compounds and will quickly die, especially from high ammonia.
Lastly, temperatures should always be on the warmer side since they live close to the equator where there is very little seasonal variation. 75-82℉ is a good range for them and if you are looking to help them fight off a disease or trying to breed them you can bump the temperature up to 85℉ to stimulate their metabolisms!
Tank Mates for Freshwater Hatchetfish
Choosing tank mates for freshwater hatchetfish should be done very carefully because these fish are very shy and retiring. In fact, no matter how long you keep them they will have a skittish aspect to them. Since hatchetfish live right near the surface and are constantly exposed to predators they need to be ready to flee at a moment’s notice.
Consider fish that are their size or even smaller. Not only are hatchetfish not aggressive but their mouths are so tiny that they would only be a threat to something like newborn guppies or fish eggs. Nothing larger is edible to them and will usually be ignored.
Be careful with fish that show intraspecific aggression towards one another though, such as Dwarf Cichlids. They can work since all cichlids occupy the bottom and midwater regions of the tank while hatchetfish stay right at the surface of the tank. But an aggressive chase between cichlids could cause your hatchetfish to try leaping, which is never good.
Guppies, Dwarf Gouramis, Tetras, Dwarf Otocinclus, Chili Rasboras, Cherry Barbs, and other small, gentle fish are by far the best tank mates for freshwater hatchetfish. Give them free reign of the surface and avoid other surface dwellers like Killifish and African Butterflyfish unless you are certain that they won’t bother your hatchetfish.
Lastly, other hatchetfish of the same species make excellent tank mates. In fact, your freshwater hatchetfish would probably be happiest if you just gave them a tank to themselves with no one else around!
Good Tank Mates for Freshwater Hatchetfish:
- Dwarf Gouramis, Guppies, Platies, Tetras, Dwarf Otocinclus, Rasboras, Corydoras, Kuhli Loaches, smaller Barbs, Discus, Angelfish, and other Peaceful Community Fish
- Other Hatchetfish
- Dwarf Shrimp, Snails, Clams, and other Invertebrates
- Dwarf Cichlids (with caution)
Poor Tank Mates for Freshwater Hatchetfish:
- Bettas, larger Gouramis, Cichlids, and other Semi-Aggressive to Aggressive Fish
- Any Large, Predatory Fish
Hatchet Fish Diet
Feeding hatchetfish can be a little more challenging than you might expect if they have been wild caught. Wild caught fish often don’t recognize flakes or pellets as food, especially carnivorous fish like hatchetfish. They are looking for the wiggle of prey to engage them and won’t eat unmoving dead things.
So ask to see any hatchetfish at your local pet store before buying them unless you are confident you can wean them onto flakes and frozen food yourself. Unfortunately wild fish can sometimes starve before learning to eat dead and prepared food.
Assuming your hatchetfish aren’t so picky you can provide them with a wide range of carnivorous options! Hatchetfish are known as “micro predators,” meaning they feed on tiny animals they find in nature. In fact they specialize in insects living near the surface so mosquito larvae and bloodworms are some of the best food choices you can offer them!
However they will also accept brine shrimp, daphnia, micro worms and other small items. Giant Hatchetfish can also eat tubifex and blackworms with ease.
Any prepared food you offer them should be very high in protein, with whole fish, shrimp, krill, or other animal matter as the foundation. Stay away from vegetable based formulas, which won’t taste right and won’t provide hatchetfish with the right nutrition.
Breeding Hatchetfish
Breeding hatchetfish is a unique challenge and something few aquarists ever manage to do on purpose. Since the hatchetfish live in schools of hundreds of individuals they are unlikely to feel comfortable enough to spawn in your tank.
What’s more, they live in the wild where seasonal cues in water chemistry and temperature influence hatchetfish reproduction. They also have a richer diet thanks to all of the unprepared options that hit the water.
That said, breeding hatchetfish is not impossible, it’s just mostly luck combined with providing your freshwater hatchetfish with the best possible conditions! Since male and female common hatchetfish look identical to one another you will need to buy several to have any chance at all. The females will plump up slightly as eggs build up within but not in a dramatic fashion, like a livebearer would.
Hatchetfish are egg scatterers and are most likely to spawn in tanks full of live plants. Plants provide an ideal place for the sticky eggs to adhere to and remain hidden until the fry hatch.
Here is a video of freshwater hatchetfish spawning and releasing eggs in a fish tank! Notice how identical in size and color the male and female are.
One thing you’ll notice is that these hatchetfish don’t lay their eggs directly onto the plants; they just broadcast them into the water. Normally the currents would pick up the eggs and carry them onto plants.
But it’s much more likely in a tank like this for your filter to suck up any eggs in the water. Yet another reason why heavily planted aquascapes are the tanks where hatchetfish are the most likely to breed for aquarists!
Frequently Asked Questions about Hatchetfish
Here are some frequently asked questions about hatchetfish of all kinds!
Hatchetfish are the exact opposite of aggressive. They are peaceful and even shy community fish that should only be kept with other gentle fish. Aggressive tank mates will cause them stress and they may even try leaping out of the water in response to an attack.
Freshwater hatchetfish size depends on the species of hatchetfish you have. Pygmy hatchetfish are the smallest, rarely growing larger than 1 inch. On the other hand, the Giant Hatchetfish grows to 3 inches maximum. Marbled Hatchetfish, Silver Hatchetfish, and other species fall somewhere in between!
You can keep a wide variety of fish with hatchetfish; just choose species that are calm and peaceful. Neon Tetras, Dwarf Gouramis, Cherry Barbs, and Guppies are some of the fish that can live with hatchetfish!
Hatchetfish are carnivorous and sometimes very picky eaters. Be prepared for newly wild caught specimens to go on a hunger strike until they understand what prepared food is. Feed newly caught hatchetfish daphnia, brine shrimp, blood worms, and other small live prey and try gradually weaning them onto frozen and prepared food!
