Penguin tetra
Thayeria boehlkei
easy careOverview
The penguin tetra (Thayeria boehlkei) is instantly recognisable for two things: the bold black stripe that runs down its side and into the lower tail lobe, and its habit of hanging in the water at a distinct head-up angle. That “penguin” posture is entirely natural. Hardy, active and adaptable, it’s an easy, slightly quirky shoaling fish that brings movement and a graphic black-and-silver look to a community tank.
Tank & water
An active, medium-sized tetra that needs swimming room and numbers:
- A cycled tank of at least 75 litres — cycle the aquarium before stocking and check how many fish in an aquarium.
- Temperature 22–28 °C with a reliable heater.
- Soft to hard water (pH 6.0–8.0) — their wide tolerance makes them easy. Moderate filtration; they enjoy a little flow.
- A planted layout with open space — plants at the sides and clear water in the middle for their busy swimming.
Feeding
Penguin tetras are active omnivores. A staple tropical flake or micro-pellet, plus frozen or live daphnia, brine shrimp and bloodworm, keeps them healthy and well-coloured. They feed across the water column, so mix floating and sinking foods. Feed small amounts once or twice a day. See the fish food and best fish food guides.
Tankmates
Peaceful in a group, penguin tetras suit lively community tanks with robust, short-finned fish — other active tetras like black skirt and serpae tetras, danios, barbs, rasboras and corydoras. Avoid slow or long-finned species such as bettas, guppies and angelfish. Matched with sturdy tankmates and kept in numbers, they’re an easy, eye-catching shoal.
For a stable, planted community with swimming room, our best aquarium for beginners guide covers the essentials — penguin tetras add motion and a striking silhouette to any mixed tank.
Penguin tetra — frequently asked questions
Why do penguin tetras swim at an angle?
It's completely normal — penguin tetras naturally hold themselves head-up, tail-down at roughly a 30-degree angle, both at rest and when swimming. It's a species trait, not a sign of illness or swim-bladder trouble, and it's part of their charm.
Are penguin tetras easy to keep?
Yes. They're hardy, adaptable to a wide pH range and undemanding once the tank is cycled, which makes them a good, slightly unusual community fish. Keep a shoal of six or more in a planted tank and they're straightforward.
Do penguin tetras nip fins?
They can, particularly in small groups or with slow, long-finned tankmates. A shoal of six or more and active, short-finned companions keep the nipping in check. Avoid housing them with bettas, guppies or angelfish.
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