Halfbeak Care Guide: Keeping the Wrestling Halfbeak (Dermogenys pusilla)
With its long, spear-like lower jaw and habit of cruising just beneath the water's surface, the halfbeak is one of the most distinctive livebearers in the hobby. The most common aquarium species is the wrestling halfbeak (Dermogenys pusilla), a slender, active little fish named for the jaw-locking sparring matches the males stage with one another. They're a rewarding choice for hobbyists who want something a little off the beaten path.
This guide covers everything we'd walk a customer through at the shop: tank setup, water parameters, that surface-focused diet, livebearer breeding, and the right tankmates. One quick heads-up first — we don't currently stock halfbeaks at Tropical Treasures, but we carry plenty of related livebearers, and we're always happy to special-order fish for you. Just ask!
Halfbeak at a glance 📋
Most aquarium halfbeaks stay small, around 2.5–3 inches, with that signature elongated lower jaw. They are surface-oriented livebearers, meaning they give birth to live fry rather than scattering eggs. Peaceful toward other species but a little skittish, they do best in calm, well-covered tanks. With good care they typically live 2–3 years.
Tank size & setup 🌿
A trio or small group of halfbeaks does well in a 20-gallon long or larger — they value swimming length and surface area over height. Because they live right at the top, the single most important piece of equipment is a tight-fitting lid; halfbeaks are nervous fish that dart and jump when startled, so cover every gap.
Keep flow gentle and the surface calm. Floating plants are a huge help — they provide security, dim the light, and give the fish a place to feel hidden. Browse our floating plants and wider live plant selection, pair them with a soft substrate, and choose a gentle filter that won't churn the top of the tank.
Water parameters 💧
Wrestling halfbeaks are adaptable but appreciate stable, slightly hard, neutral-to-alkaline water. Aim for 72–82°F with a pH around 7.0–8.0. Many keepers find a touch of aquarium salt or harder water helps them settle, though it isn't strictly required. Above all they want clean, stable conditions — sudden swings stress them quickly, so keep up with regular small water changes.
Diet & feeding 🍚
Halfbeaks are surface feeders with small mouths built for snapping up insects and tiny prey from the film. They do best on small floating foods: micro pellets, finely crushed flakes, and especially live or frozen treats like fruit flies, mosquito larvae, daphnia, and baby brine shrimp. Our frozen foods and floating flakes make good staples — variety keeps them colorful and healthy.
Temperament & tankmates 🤝
Halfbeaks are peaceful but timid, and they stick to the top of the tank. The ideal community keeps the surface calm and fills the middle and lower levels with equally gentle fish. Avoid anything boisterous, fin-nippy, or large enough to harass them — and skip very tiny fish or shrimp that might be mistaken for food.
Good in-stock companions at the shop include peaceful livebearers like a fancy guppy or endler that stay out of the surface zone, calm swordtails from our swordtail collection, or a small school of mid-water silvertip tetras. Browse our guppy and endler collections for more peaceful options.
Breeding 🥚
Like other livebearers, halfbeaks deliver free-swimming fry rather than laying eggs — but they're trickier than guppies. Females carry for several weeks and produce small broods, and they can be prone to dropping fry prematurely if stressed, so keep them calm and well-fed. Dense floating plants give the fry somewhere to hide, and feeding tiny live foods like baby brine shrimp gives them the best start. If you enjoy livebearer breeding, our Humpback Limia guide covers another fun project.
Common care notes ⚠️
The two things new halfbeak keepers underestimate are jumping and stress. Keep that lid sealed, give them floating cover, and introduce them to a mature, stable tank rather than a brand-new setup. They can be sensitive during acclimation, so go slow. For a refresher on avoiding the usual beginner pitfalls, see our common mistakes guide.
Is the halfbeak right for you? 🤔
Halfbeaks suit keepers who want something unusual, enjoy a calm planted tank, and don't mind offering small live or frozen foods. If you'd rather have a bustling, beginner-friendly community, a guppy or tetra tank is an easier start — check our freshwater tetra guide for ideas. But if a surface-cruising livebearer with a built-in spear sounds appealing, halfbeaks are full of personality. For setting up that all-important surface cover, see our floating plants guide.
The bottom line
The wrestling halfbeak is a charming, surface-loving livebearer that brings a different look and a fun set of behaviors to a peaceful planted tank. Give it length, floating plants, a tight lid, small floating foods, and calm tankmates, and it'll thrive. We don't always have halfbeaks on hand, so stop by Tropical Treasures in Cheyenne (307-369-1118) or give us a call and we'll help you build the setup — and look into sourcing one for you.