Silver Hatchetfish
Gasteropelecus sternicla
Min Tank Size
75L
Adult Size
6.5 cm
Lifespan
5 years
School Size
6+
About
Native to slow-moving and still blackwater rivers and streams across much of South America, the Silver Hatchetfish is one of those fish that looks almost sculpted rather than evolved. That deep, keel-shaped chest is packed with powerful pectoral muscles that allow it to break the surface and glide short distances through the air, a genuine adaptation for escaping predators in the wild, not just a party trick in your aquarium.
They stay almost exclusively at the surface, hanging just under the waterline and watching for insects to fall from overhanging vegetation. In captivity, this means they're feeding from the top or just below it, and they won't compete with mid-water or bottom-dwelling species for food at all.
Water conditions matter a lot here. Soft, slightly acidic water in the 6.0 to 6.8 pH range is where they thrive, and they don't adapt well to hard, alkaline conditions over the long term. Tannin-stained water from driftwood or Indian almond leaves isn't just aesthetic, it genuinely helps them settle in.
Diet is an area where beginners sometimes struggle. These are insectivores at heart, and while they can learn to accept quality floating flake or micro pellets, they do best with regular offerings of fruit flies, frozen bloodworms, or small crickets. A group kept entirely on dry food often stays thin and subdued. Feed at the surface and watch them compete eagerly for anything that lands on the water.
Silver Hatchetfish are a genuinely rewarding community fish if their needs are met, especially in a planted setup with floating plants and a dark substrate that encourages natural behavior. Browse Shimmerscape to find real tank builds featuring this species alongside the companions that work best with them.
Water Parameters
Temperature
°CpH
GH
dGHKH
dKHSwimming Level
Flow Preference
Keeping multiple Silver Hatchetfish together
Silver Hatchetfish are shoaling fish and need company of their own kind. Keep a group of at least 6. Smaller groups leave them stressed, washed-out in color, and prone to hiding.
Compatibility
These fish occupy the top of the water column exclusively, which makes them exceptionally easy to pair with species in lower zones. Cardinal or neon tetras, corydoras, dwarf cichlids like apistogramma, small loaches, and pencilfish all work well without any competition for space or food. Avoid large, boisterous tankmates that will startle them constantly, and skip any cichlids with a reputation for surface harassment. Gouramis can sometimes be an issue since they also cruise the top layer. They're fine with small shrimp and snails, posing no threat to either. A 75-liter tank works for a small group, but a 100-liter or larger lets the school move freely and behave more naturally.
Commonly kept with
Species this one is most often paired withCommonly tried but avoid
Often paired, but shouldn't beCare Notes
The two things that kill hatchetfish fastest are an uncovered tank and poor water quality. A gap of even a few centimeters is enough for them to escape, and they will, especially at night. Beyond the lid, they're surprisingly sensitive to nitrates and dissolved organics, so they really need a mature, cycled tank with consistent water changes. New tank syndrome takes them out quickly. Beginners also underestimate how important surface movement is. Gentle surface agitation keeps oxygen levels up right where these fish live, but strong flow stresses them. Aim for turnover that creates ripple without current.
Behavior & Aggression
Silver Hatchetfish are about as peaceful as a fish gets. There's no aggression toward tankmates of any kind, and conspecific interactions are mostly limited to mild jostling within the school at feeding time. They don't nip fins, they don't establish territories, and they won't bother anything sharing their tank. The only stress-related behavior worth watching is when the group is too small. A school of fewer than six can become skittish and erratic, which sometimes leads to jumping, but that's anxiety, not aggression.
Things to Know
- Tight-fitting lid is mandatory, they jump constantly and will not survive without one
- Keep in groups of 6 or more, lone individuals decline quickly
- Very sensitive to water quality, they're often first to show signs of deterioration
- Wild-caught specimens may refuse dry food initially, start with live or frozen insects
- Can be skittish, avoid sudden movements near the tank
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