Hatchetfish Care Guide
Hatchetfish are one of the aquarium hobby’s most distinctive surface dwellers, named for the deep, blade-like keel of their chest that gives them a hatchet-shaped silhouette. These peaceful schooling characins spend their lives just beneath the water’s surface, where their unusually large pectoral fins let them perform their signature trick: short, gliding leaps that have earned them a reputation as the closest thing to a flying fish in freshwater. We carry the beautifully patterned Marble Hatchetfish (Carnegiella strigata) and the larger Silver Hatchetfish (Gasteropelecus levis). One honest note up front, and it is the most important point on this page: hatchetfish are champion jumpers, so a tight-fitting lid with no gaps is absolutely essential to keep them in the tank.
Meet the Hatchetfish
Hatchetfish come from the slow, shaded streams and flooded forests of South America and are close relatives of tetras. The marble hatchetfish is a true nano fish at around 1.5 inches, while the silver hatchetfish is a bit larger at 2 to 2.5 inches. They are strictly top-dwelling fish, hovering near the surface to watch for insects, and they are happiest in a calm, well-covered tank that mimics their wild home. Because they live in the upper inch or two of water, they occupy a layer of the aquarium that many community fish ignore, making them a wonderful way to add life to the top of a planted community tank.
Tank Size and Setup
A school of hatchetfish does well in a 20-gallon long, which provides the surface area they care about most. Surface space matters far more than depth for these fish. The most critical piece of equipment is a tight, gap-free lid: hatchetfish will leap at the slightest disturbance and can shoot through tiny openings around filters and cords, so cover everything. Beyond that, recreate their shaded habitat with floating plants to diffuse the light and give them cover overhead, plus tall live plants and driftwood. A gentle filter that keeps the surface calm is ideal, as they dislike strong current. A darker substrate and dim lighting help them feel secure and show their best colors.
Water Parameters and Heating
Hatchetfish are tropical fish that need warm, stable water of 75-82°F from a reliable aquarium heater. They come from soft, acidic blackwater and look and feel their best at a pH between 5.5 and 7.0, though tank-raised fish adapt to slightly harder water. They can be a little sensitive when first introduced, so stability is key: always add them to a fully matured tank that has completed the nitrogen cycle, treat tap water with a water conditioner, and keep conditions pristine with regular water changes using your maintenance supplies. Adding driftwood or botanicals to gently tint the water mimics their natural environment and can help them settle in.
Feeding Your Hatchetfish
Here is the single most important feeding fact: hatchetfish are surface feeders with upturned mouths designed to take food from the top of the water, and they will rarely if ever go to the bottom to eat. Choose foods that float or stay at the surface, such as floating flakes and small floating pellets. In the wild they are insectivores, so they relish small live and frozen foods like fruit flies, daphnia, and baby brine shrimp, which bring out their best color and natural behavior. Round out the diet with a quality staple food, and feed small amounts so the food is eaten before it sinks out of reach.
Tankmates and Temperament
Hatchetfish are extremely peaceful and a little timid, so they should only be kept with other calm, non-aggressive fish. Because they occupy the very top of the tank, they pair beautifully with mid- and bottom-dwelling species that leave the surface to them, such as tetras, peaceful rasboras, corydoras catfish, and dwarf shrimp. Avoid large, boisterous, or fin-nipping fish that will stress them or outcompete them at the surface. Crucially, hatchetfish are schooling fish and must be kept in a group of at least 6, and ideally 8 or more; in a proper school they are calmer, bolder, and far less likely to make panicked leaps.
Health and Behavior
Hatchetfish are reasonably hardy once settled but can be sensitive during the first weeks in a new tank, so acclimate them slowly and only add them to an established aquarium. Their flat, keeled shape makes them prone to nothing unusual, but their jumping does: the most common cause of loss is simply finding one on the floor, which a secure lid prevents. Watch for clamped fins or rapid breathing as early signs of stress or poor water quality, and keep their environment calm and stable. Skittish behavior, surface dashing, and refusing to eat usually trace back to too-small a group, an open tank, or a tankmate that is too rowdy.
Is a Hatchetfish Right for You?
Hatchetfish are a perfect choice if you want something unusual and elegant to animate the top of a peaceful, well-planted community tank, and if you can commit to a tightly covered aquarium. They are not the best fit for open-top tanks, rowdy communities, or anyone wanting a fish that forages all over the tank. If you are still planning your stocking, our guides on the best nano fish for planted tanks and best beginner fish pair well with them. When you are ready to add a touch of the exotic to your surface, browse our available hatchetfish in the nano fish collection.
Frequently Asked Questions
Do hatchetfish really jump? Yes, famously so. Their large pectoral fins let them glide several inches out of the water, and they leap when startled. A tight, gap-free lid is essential to keep them safely in the tank.
How many hatchetfish should I keep? Keep at least 6, and ideally 8 or more. They are schooling fish that feel secure, behave naturally, and jump far less when kept in a proper group.
What do hatchetfish eat? They are surface-feeding insectivores. Offer floating flakes and small floating pellets, plus live or frozen foods like daphnia, fruit flies, and baby brine shrimp. They will not feed off the bottom.