Penguin Tetra Identification Guide
Identify the penguin tetra by its bold black stripe that angles down into the lower lobe of the tail fin.
Read the full Penguin Tetra encyclopedia entry →
Key identification features
- Slender, torpedo-shaped body about 2 inches (5 cm) long with a silvery-olive back
- Thick black horizontal stripe starting near mid-body and angling down through the lower caudal fin lobe
- Upper caudal lobe remains pale and clear, creating an asymmetric tail pattern unusual among common tetras
- Often swims at a distinctive head-up, tail-down angle
- Small, unmarked adipose fin
Common look-alikes
- Black skirt tetra: has a black-fringed, fan-shaped anal and tail area but lacks the penguin tetra's single stripe confined to the lower tail lobe.
- Emperor tetra: shows a full-length dark lateral stripe across the entire body and tail rather than one limited mainly to the lower caudal lobe.
- Head-and-tail-light tetra: has separate reflective spots at the shoulder and tail base instead of one continuous stripe.
Where you'll see one
Found in slow, blackwater and clearwater tributaries of the Amazon basin in Peru and Brazil, it schools in open mid-water among submerged wood and vegetation, generally staying in tight, coordinated groups.
Frequently asked questions
What is the single clearest mark of a penguin tetra?
A bold black stripe that runs only into the lower lobe of the tail fin, leaving the upper lobe pale.
How does its swimming posture help with identification?
It characteristically holds its head tilted upward and tail down, unlike most level-swimming tetras.