Care Guide for Hatchetfish – Oddball Schooling Fish with Wings

Most freshwater fish like to hang out in the lower two-thirds of the aquarium, so it can be hard to fill in the upper third with some activity. Enter the hatchetfish. This top-dwelling nano fish has a very unique appearance that looks even cooler when you have a large school darting around just beneath the water surface. However, they have some special care requirements to be aware of, so let’s take a closer look at this interesting oddball.

What are Hatchetfish?

Freshwater hatchetfish come from the Gasteropelecidae family and are distantly related to tetras. They can be found all over South and Central America and are known for having a hatchet-shaped body and pectoral fins that extend out from the body like bird wings. Their strong pectoral muscles enable the hatchetfish to jump several inches out of the water, allowing them to quickly escape predators.

What are the different types of hatchet fish? Several species are sold at local fish stores, but their availability may be seasonal. They usually range from 1–2.5 inches (2.5–6 cm) long, so we have listed them roughly in order of smallest to biggest size.

• Pygmy hatchetfish (Carnegiella myersi)
• Blackwing hatchetfish (Carnegiella marthae)
• Marbled hatchetfish (Carnegiella strigata)
• Silver hatchetfish (Gasteropelecus levis)
• Common hatchetfish (Gasteropelecus sternicla)
• Spotted hatchetfish (Gasteropelecus maculatus)
• Platinum or spotfin hatchetfish (Thoracocharax stellatus)

Marbled hatchetfish (Carnegiella strigata)

While some species like the common hatchetfish are now available as captive-bred or tank-raised, most hatchetfish are caught from the wild. By the time they travel from the wholesaler to the fish store, they may be underfed with weakened immune systems, making them more susceptible to disease. Ask the fish store how long they’ve had the hatchetfish, watch them eat, and observe their behavior before making a purchase.

We strongly recommend that you always quarantine hatchetfish, feed them lots of high-quality foods, and proactively treat them with the trio of quarantine medications if possible. Hatchetfish are prone to ich or white spot disease, which is easily cured with Aquarium Solutions Ich-X. Also, wild-caught fish often have internal parasites like tapeworms, so treat them with Fritz ParaCleanse and then treat them again two weeks later to eliminate any worm eggs that hatched.

How to Set Up an Aquarium for Hatchetfish

Hatchetfish can live in a wide range of pH, GH, and other water parameters because their habitat experiences rainy seasons and flooding every year. They are tropical animals that thrive in temperatures between 75–80°F (24–27°C). As a schooling fish, they need to be in a big group of at least 6–12 fish of the same species. The more fish in their school, the safer they feel and the more comfortable they are displaying their natural behaviors. For example, our CEO Cory McElroy once owned a group of 30 silver hatchetfish, and when they changed directions at the same time, he would see a bright flash of light as their scales reflected like little mirrors.

A school of hatchetfish in a blackwater aquarium

Hatchetfish are not super active, so you can keep them in a 20-gallon aquarium or larger. The tank must have a tight-fitting lid or hood because they will jump out of the narrowest slot they can find. If you have any openings for the filter, heater, or automatic fish food feeder, make sure to cover them with craft mesh or another material.

What fish can live with hatchet fish? Avoid keeping hatchetfish with other fish that are aggressive, large enough to eat them, or fast-swimming and able to outcompete them for food. They do best with tank mates that are similar-sized and peaceful, such as tetras and corydoras catfish. South American dwarf cichlids like German blue rams and Apistogramma cichlids are also fine because they occupy the lower half of the tank, while hatchetfish stay up above.

What Do Hatchetfish Eat?

One of the main problems that fishkeepers have with hatchetfish, especially as they get bigger, is underfeeding because they really prefer to eat from the water surface and do not like swimming down to get sinking foods. In the wild, they use their small, upward-facing mouths to feed on insects and zooplankton. Therefore, feed tiny foods that float for a long time, and decrease water flow near the surface so the food won’t sink as quickly. Good floating foods include high-quality flakes, floating pellets, freeze-dried foods, and live baby brine shrimp that tend to swim toward the aquarium light.

Platinum hatchetfish (Thoracocharax stellatus)

We hope you will try the incredible hatchetfish and enjoy its unusual appearance and behavior. For more ideas on other surface dwellers to try, check out our article on the 10 Best Top-Dwelling Fish for Your Aquarium.