Silver Hatchetfish (Thoracocharax securis)

Choose the Silver Hatchetfish for the top of a calm, planted tank

The Silver Hatchetfish, Thoracocharax securis, is a large Amazonian hatchetfish with a deep, keeled chest that gives it the shape of a hatchet blade. Its body is bright silver with a scatter of fine dark speckles and a soft gold sheen along the back, the eye is large and dark, and the long, wing-like pectoral fins sit high on the chest. It spends its life in the upper water, so it fills a part of the aquarium most fish ignore.

FishBase calls this species the giant hatchetfish and gives it 6.8 cm standard length in the wild and up to 9 cm in aquariums, which is large for a hatchetfish. Wikipedia notes that it is rarely seen in the hobby. It is peaceful and nervous, feeds mainly at the surface and needs a group of its own kind, a long tank with plenty of surface area and, above all, a tight lid.

A settled group hangs together just below the surface or in the top third of the water, holding position with small movements of the fins, then dashes up the moment food lands. It makes a calm, unusual addition to a peaceful South American community.

Check the fit before you order

The Silver Hatchetfish sits with our tetras and characins, and you can browse related species in our South American tetra category.

Know what one purchase supplies

One purchase quantity supplies one live Silver Hatchetfish. The only option is “Small”, the size grade the fish are sent at, so they are likely to arrive well short of adult size and grow on in your aquarium. The photographs show the species, not the individual fish you will receive. Sex is not specified.

Seriously Fish describes Thoracocharax as nervous, so a calm arrival matters. Have the aquarium mature, heated, tested and fitted with a lid before the fish arrive, and read our delivery and live arrival terms before ordering.

Plan the group before you buy

• Six or more: FishBase gives groups of five or more; Seriously Fish advises at least half a dozen for Thoracocharax and says they will not settle without their own kind.
• Buy together: a group added at once settles faster and feeds sooner.
• Check space: use our tank volume calculator and remember that surface area matters more than depth for this fish.

Understand the name and tell it apart

Hatchetfish belong to the family Gasteropelecidae, the freshwater hatchetfishes. Seriously Fish lists three genera: Carnegiella with four species, Gasteropelecus with three and Thoracocharax with two. This fish was described in 1853 by De Filippi as Gasteropelecus securis, and Wikipedia also lists Gasteropelecus pectorosus as a synonym. The genus Thoracocharax was raised to full genus rank in 1960. FishBase gives its range as the Amazon basin and assesses it as Least Concern on the IUCN Red List.

“Silver hatchetfish” is a trade name used for more than one species. We also sell the Silver Hatchetfish Gasteropelecus sternicla, a smaller fish from a different genus, so always check the scientific name when you compare.

Compare it with its closest relative

The only other Thoracocharax is the Spotfin Hatchetfish, Thoracocharax stellatus. Seriously Fish notes that the two look alike, but the Spotfin Hatchetfish has a prominent dark spot in the dorsal fin, which Thoracocharax securis lacks. Our photographs show the clear dorsal fin without that spot.

Plan the aquarium around the surface

FishBase gives a minimum aquarium length of 100 cm for this species. Seriously Fish has no separate profile for T. securis, but for its close relative it recommends a surface of at least 120 × 45 cm as the smallest worth considering. Hatchetfish live at the top of the water, so a long, wide tank with a big surface suits them far better than a tall one. OATA’s UK care sheet for tetras sets 80 litres as the minimum for species of 5 cm or more.

The lid is the single most important piece of equipment. FishBase warns that the species may jump out of the aquarium, and Seriously Fish says Thoracocharax can clear several metres in a single leap and that a lid left open overnight often means a fish on the floor by morning. Wikipedia cites glides of up to 2.74 metres, although Seriously Fish points to research showing that hatchetfish use their pectoral fins to leave the water in a powerful jump rather than to fly.

Use a three-step space check

1. Surface first: 100–120 cm long and as wide as you can manage.
2. Lid: tight-fitting, with cable gaps and feeding hatches closed.
3. Air gap: leave a few centimetres between the water and the lid so the fish can surface-feed without striking the cover.

Arrange floating cover and quiet water

Seriously Fish recommends covering a good part of the surface with floating plants for Thoracocharax, which makes these flighty fish less nervous. It adds that they like some current to swim against now and then but also need quiet areas, and that Thoracocharax tends to sit in the upper third of the water rather than right at the surface like Carnegiella. Decor below is not critical; a planted tank or an Amazon-style layout with wood, sand and leaf litter works well.

Our aquarium plants range includes floating and background plants for this kind of set-up.

Divide the footprint by function

Match the water values

FishBase gives 23–30°C, pH 6.0–7.5 and hardness up to 15 dH for Thoracocharax securis. Seriously Fish gives 20–28°C, pH 5.0–7.5 and 1–12 dGH for its close relative, and OATA’s general guidance for tetras is 22–27°C, pH 6.5–8.0 and 4–12°dH. The values that satisfy all three are 23–27°C, pH 6.5–7.5 and 4–12 dGH, so that is what we recommend.

UK tap water ranges from soft to very hard. Test your own supply and use our water matcher to see how it compares; softer water suits this species best. Always use a tap water conditioner to remove chlorine or chloramine.

Use these values as a checklist

Our water chemistry guide explains each reading and how to test it.

Keep the water clean without disturbing the surface

OATA recommends testing at least weekly, changing about 25% of the water every week with conditioned replacement water, and rinsing filter media only in removed tank water. Seriously Fish suggests filtration that turns the tank over four to five times an hour for Thoracocharax. Direct the outlet so it ripples part of the surface without turning the whole top of the tank into a current.

Follow a weekly maintenance sequence

1. Test ammonia, nitrite, nitrate and pH.
2. Slide the lid back only as far as you need, and work slowly to avoid startling the group.
3. Siphon out about 25% of the water and refill with conditioned water at the same temperature.
4. Thin floating plants so they cover part of the surface, not all of it.
5. Close and check the lid before you walk away.

Feed insect foods at the surface

Seriously Fish reports a study by Netto-Ferreira and colleagues (2007) in which 99.6% of the diet of Thoracocharax was insects, 87.6% of them land insects that had fallen onto the water. It feeds near the bank from the surface but will dip down for sinking food, and may refuse dried food at first before learning to accept it. Seriously Fish recommends a large share of live and frozen foods such as bloodworm and daphnia, and calls gut-loaded fruit flies excellent when available. OATA advises feeding once a day, only what the fish eat within a few minutes.

A fruit fly culture gives the closest thing to wild food. For everyday meals use insect granules with frozen daphnia and live bloodworms in rotation.

Build one measured meal

• Small and often: one or two small meals a day, cleared within a few minutes.
• At the surface: scatter food across the open strip so every fish can reach it.
• Insects first: live or frozen insect foods on most days, especially in the first weeks.
• Feed the bottom too: drop sinking food for bottom-dwellers at the same time so they do not rise to compete.

Acclimatise new fish with the lights off

Follow OATA’s floating-bag method, with the lid in place as much as possible:

1. Switch off the aquarium and room lights.
2. Float the sealed bag for 10 minutes to match the temperature.
3. Add small amounts of tank water to the bag over up to 20 minutes.
4. Net the fish gently into the tank and close the lid straight away.
5. Dispose of the bag water down a household drain.

Our article on how to acclimate new fish covers the same routine.

Use a first-week checkpoint plan

Watch the group and act on changes

Healthy hatchetfish hold a steady position in the upper water, keep their fins spread and rise quickly to food. OATA lists the warning signs: colour much paler or darker than usual, more hiding, faster breathing, white spots or fluffy growths, damaged fins and loss of appetite. Because hatchetfish compete poorly for food, check every fish at feeding time and watch for a pinched, hollow belly.

Pair each observation with an action

Choose calm tank mates for the lower levels

Seriously Fish describes Thoracocharax as very peaceful but nervous, and notes that it does not compete well for food with boisterous species. It recommends tank mates that use different levels of the aquarium: tetras in the middle, bottom-dwelling cichlids such as Geophagus and Satanoperca, and catfish such as Corydoras and plecos. Good choices include Rummy Nose Tetras, Three-Lined Pencilfish, Sterbai Corydoras and, in a large tank, the Demon Eartheater. The smaller Marbled Hatchetfish shares the surface peacefully in a big enough tank. Run any other choice through our tank mates checker.

Screen every companion

For more ideas, browse our schooling fish.

Breeding notes

Breeding has not been recorded for Thoracocharax in aquariums, according to Seriously Fish. The only visible sex difference it reports is that females are noticeably rounder-bodied when full of eggs. OATA notes that tetras and their relatives are egg scatterers and that home breeding needs a dedicated set-up and specialist fry food, so treat any spawning as a bonus rather than a goal.

Never release fish or tank water

OATA reminds keepers never to release aquarium fish or plants into the wild: it is illegal, usually fatal to the fish and can harm native wildlife. Dispose of water, substrate and plant trimmings through the drain or household waste.

Answer Silver Hatchetfish buying questions

Which hatchetfish is this?

This is Thoracocharax securis, a large Amazonian hatchetfish that FishBase calls the giant hatchetfish. “Silver hatchetfish” is a trade name used for more than one species, including Gasteropelecus sternicla, so check the scientific name when you compare listings.

How is it different from the Spotfin Hatchetfish?

The two are the only species in the genus Thoracocharax and look alike. Seriously Fish notes that the Spotfin Hatchetfish, Thoracocharax stellatus, has a prominent dark spot in the dorsal fin, which Thoracocharax securis lacks.

How big does it get?

FishBase gives 6.8 cm standard length in the wild and up to 9 cm total length for aquarium fish. That makes it one of the larger hatchetfish in the hobby.

Do hatchetfish really jump?

Yes. FishBase warns that this species may jump out of the aquarium, and Seriously Fish says Thoracocharax can leap several metres. A tight-fitting lid with no gaps is essential.

How many should I keep?

At least six, and more is better. FishBase gives groups of five or more, and Seriously Fish says Thoracocharax will not settle without its own kind. One purchase supplies one fish.

What do silver hatchetfish eat?

In the wild Thoracocharax feeds almost entirely on insects, most of them land insects that fall on the water. Offer floating insect-based foods, frozen bloodworm and daphnia, and live fruit flies when you can. Some fish refuse dried food at first.

What tank size does it need?

FishBase gives a minimum aquarium length of 100 cm, and Seriously Fish suggests 120 × 45 cm for its close relative. Choose a long tank with a large surface area and a secure lid.

What fish can live with it?

Calm fish that use other levels of the tank: small and medium peaceful tetras, pencilfish, Corydoras, peaceful plecos and gentle eartheaters. Avoid boisterous surface feeders, fin-nippers and large predators.

Consult the care references

• FishBase: Thoracocharax securis (Giant hatchetfish) — family, maximum size in the wild and in aquariums, water ranges, distribution, group size, minimum aquarium length, jumping and IUCN status.
• Wikipedia: Thoracocharax securis — synonyms, distribution, size, leaping distance and rarity in the hobby.
• Seriously Fish: Thoracocharax stellatus (Spotfin Hatchetfish) — the only other Thoracocharax: how to tell the two apart, plus genus-level tank, cover, water, diet, behaviour and tank-mate advice used on this page.
• Seriously Fish: genus Thoracocharax — the two species in the genus.
• OATA: How to look after tetras and pencilfish — UK trade body care sheet: group water values, waste limits, weekly maintenance, feeding, acclimatisation and signs of ill health.
• Tropical Fish Co delivery terms and acclimatisation article — our own live arrival guidance.