Penguin Tetra
Thayeria boehlkei
Min Tank Size
75L
Adult Size
6 cm
Lifespan
5 years
School Size
6+
About
Native to the Amazon and Araguaia river basins in South America, penguin tetras have a quirky charm that sets them apart from the usual tetra crowd. That bold black stripe running from behind the gill plate all the way down into the lower lobe of the caudal fin is what earns them their name. They hold their bodies at a distinct upward angle when at rest or hovering, giving them the look of a tiny penguin standing upright. It's genuinely one of those fish you notice immediately in a mixed community tank. They grow to around 6 cm and are solidly built for a tetra, more so than neons or cardinals.
Water parameters are forgiving by South American standards. They'll thrive in slightly acidic to neutral water with a pH of 6.0 to 7.5 and temperatures between 22 and 28 degrees Celsius. Soft to moderately hard water suits them fine, and they're not fussy about decor, though darker substrates and some floating cover really help their colors pop.
Feeding is easy. They'll take quality flake food without hesitation, and supplementing with frozen or live daphnia, bloodworm, or brine shrimp keeps them in top condition.
They're active mid-to-upper swimmers and spend most of their time darting around in the upper half of the water column, which means they pair naturally with bottom dwellers without competition. Temperament is reliably peaceful. They don't hassle tankmates and aren't known for nipping, making them a solid pick for community setups of all kinds.
Browse real tank builds featuring penguin tetras and you'll see just how well they complement a wide variety of species and aquascape styles.
Water Parameters
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Flow Preference
Keeping multiple Penguin Tetra together
Penguin Tetra 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
Penguin tetras are excellent community fish that get along with a wide range of peaceful species. Corydoras catfish are a classic pairing since they occupy completely different water levels. Smaller rasboras, other peaceful tetras, hatchetfish, and dwarf cichlids like German blue rams or apistogrammas all work well. Avoid keeping them with very small nano shrimp like neocaridina, as there's a real possibility they'll pick off shrimplets. Amano shrimp are large enough to hold their own. Large or semi-aggressive fish like tiger barbs or larger cichlids should be avoided. A 60-liter tank works for a small school, but 80 liters or more gives them proper room to display their energetic schooling behavior.
Commonly kept with
Species this one is most often paired withCommonly tried but avoid
Often paired, but shouldn't beCare Notes
The most common beginner mistake is keeping too few of them. A group of three looks stressed and hides constantly. Six is the real minimum, and eight to ten is where their schooling behavior becomes genuinely impressive. They're not fussy about water chemistry within their range, but they do appreciate stable conditions, so avoid tanks that haven't finished cycling. A lid is non-negotiable since they're prone to jumping, especially when startled. Diet variety helps long-term health since an all-flake diet can lead to dull coloration over time. Frozen foods once or twice a week makes a noticeable difference.
Behavior & Aggression
Penguin tetras are about as peaceful as tetras get. There's virtually no aggression toward other species, and within their own group the occasional chase is more social jostling than genuine conflict. Keeping them in groups of at least six significantly reduces any skittish or frantic behavior that can be mistaken for aggression. Undersized groups sometimes result in one or two fish being persistently harassed by others, so a proper school size matters. They don't defend territory, show no interest in nipping fins, and generally mind their own business in a well-stocked tank.
Things to Know
- Keep in groups of 6+, small groups cause skittish behavior and stress
- May pick at dwarf shrimp fry, safer with larger shrimp like Amanos
- Active jumpers, a tight-fitting lid is strongly recommended
- Their angled swimming posture is normal, not a sign of illness.
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