Should I buy it?
Penguin tetra
Thayeria boehlkei
Also known as: hockey-stick tetra
A 6 cm tetra with a bold black diagonal stripe and constant waggle swimming. Peaceful and hardy in a proper school.
Penguin tetra tank mates · 80L tank size hub
peaceful · beginner care
Sources & confidencehigh · partially verified · beginner: good
Checked against several solid care sources that mostly agree. Numbers here are a careful starting point. Your tap water, tank size, and habits decide the rest. How we evaluate.
Best for: Community tanks 80L or more with neutral water and a school of eight alongside peaceful mid-water fish.
Avoid if: You keep fin-nipping species or your setup is under 60L.
Common mistakeBuying five penguin tetras for a crowded short tank is how the waggling school stresses everyone else. They need a proper group of six or more and lateral space for the swimming pattern that makes them interesting. Under-stocked or under-spaced, they look nervous and push calmer fish into the glass.
Top things that go wrong
- Group welfare — not a solo display fish. Plan at least **6** together for normal behaviour; smaller groups often mean stress, colour loss, or nipping depending on species.
- Shrimp & snails. Cherry shrimp and other dwarfs can coexist with peaceful small fish; baby shrimp are food for almost anything that finds them.
What most shops don't tell you
- 1.Shops pitch penguin tetras as hardy novelty tetras for any community. They are peaceful, but they still need a real school and room to swim the pattern people bought them for. A trio in a nano is not the species — it is a stressed fragment.
- 2.Kept in a tall but short tank with little horizontal swim run.
- 3.Housed with micro-rasbora fry. Penguin adults out-eat tiny foods before the fry get a shot.
- 4.A long footprint, 120 cm or more for adults, holds the full school posture. Avoid cold tanks under 22 °C.
About this species
Penguin tetras swim at an oblique head-up tilt that gives them the trade name. A long-bodied Amazon tetra that wants a long open tank, a tall school, and peaceful tank mates.
- Black phantom tetra80L min · same group, comparable tank size
- Columbian Tetra80L min · same group, comparable tank size
- Rosy Tetra80L min · same group, comparable tank size
- Rummy Nose Tetra80L min · same group, comparable tank size
- Splash tetra80L min · same group, comparable tank size
- Beckford Pencilfish60L min · same group, similar adult size
- Black Neon Tetra60L min · same group, similar adult size
- Bloodfin tetra60L min · same group, similar adult size
- Amano Shrimpalso beginner peaceful, similar tank size
- Beckford Pencilfishalso beginner peaceful, similar tank size
- Black Neon Tetraalso beginner peaceful, similar tank size
- Black phantom tetraalso beginner peaceful, similar tank size
- Bloodfin tetraalso beginner peaceful, similar tank size
- Bristlenose Plecoalso beginner peaceful, similar tank size
No reverse lookups listed yet.
Plan grid
Key limits are above. Here: pH band, swim level, bioload, and activity.
Swim zones
Care snapshot
Quick compare before you buy. Not a score of how “good” the fish is.
- Beginner ease78
- Peacefulness90
- Community fit91
- Small-tank fit100
- Hardiness76
- Energy86
Numbers are deterministic planning indices from Fishori fields — not a scientific score of your individual fish.
Example setups
Starting points only. Run the pair checker for every fish you add.
Rough 90L+ layout: one calm centrepiece, 8–12 small tetras/rasboras, 6–8 corydoras-type bottom fish — verify every name in the pair checker before buying.
Safer directions include: Boesemani Rainbowfish, Congo Tetra, Dwarf Gourami.
Prioritise 6+ of Penguin tetra in 80L+ with filtration sized for messy feeding — add only mates that already pass pair checks with this species.
Compatibility
Tank mates for Penguin tetra
Usually safer (engine GOOD): Boesemani Rainbowfish, Congo Tetra, Dwarf Gourami, Ember Tetra, Neon Tetra. Conditional (CAUTION — read the pair page before buying): Corydoras Catfish, Pea Puffer, Serpae Tetra, Tiger Barb, Yoyo Loach. Avoid (RISKY): African Cichlid, Green Terror, Jack Dempsey, Oscar. Every name links to a live pair check — the lists are a shortlist, not a stocking plan.
Usually safer
Open a pair page with this fish as the starting point.
Needs planning
Read the blocking rule on each pair page before experimenting.
Usually avoid
Do-not-stock combinations on conservative hobby rules.
Compare with
Run a real pair check: Penguin tetra + Boesemani Rainbowfish
Behaviour and temperament
Penguin tetras are peaceful midwater schoolers that look busier than neons because of the wagging swim. They rarely start fights; they create motion that bothers slow, long-finned fish in short tanks. Honest group size turns the motion into a school instead of a panic signal.
What sets them off
- Sudden crowding
- Poor water quality
Fin nipping: Not a habitual fin-nipper; stressed or crowded individuals can still test fins.
Predation: Not a predator toward similarly sized community fish; fry and dwarf shrimp are still fair game for most species.
Territory: Not strongly territorial, but still needs room so its working space does not overlap the next fish.
Planted tanks: excellent — easy plant ideas
In the glass: typical and warning signs
- A school of six or more holds midwater with the characteristic wagging swim.
- They settle into a calmer patrol in planted tanks with real lateral length.
- Constant glass pacing in a short cube means footprint failure before disease.
- A thin group that never schools is under-stocked, not “semi-aggressive.”
- Low listed risk as aggressors; they are more likely to be crowded than to bully.
- Fast motion can still provoke bettas and slow gouramis — that is layout, not tetra malice.
- Move them out of any nano where the wagging never stops and tank mates hide.
- Add to the school before you add another midwater species to “calm them down.”
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Water, food, and grouping
Hardness
medium
Diet
omnivore
Penguin tetras take flake and micro-pellets in the midwater scramble and hold condition on ordinary community foods better when a frozen or freeze-dried protein shows up a few times a week. Feed a pinch they can reach before faster surface fish clear the film. Colour and the black line stay sharper on varied food than on a single dry staple.
Shrimp & snails
Cherry shrimp and other dwarfs can coexist with peaceful small fish; baby shrimp are food for almost anything that finds them.
Schooling species — buy 6+ together. Smaller groups stress and lose colour.
- Hold 22 to 28 °C steadily on a real thermometer, not the dial on the heater.
- Aim for pH 5.5 to 7.5 and a hardness you can re-test in two weeks. A one-time strip in the shop car park is not a water test.
- Schooling species. Buy 6 or more from the same tank on the same day before adding any centrepiece fish.
- Tank volume meets or exceeds 80L published minimum for adults.
- You can stock at least 6 individuals (group welfare).
- Heater can hold 22–28°C without cooking cooler-water tank mates.
Explore and stocking hubs
Tank-mates hub, matching guides, category peers, and litre stocking lists around this species’ minimum tank.
Plan with tools
Check mates as pairs first, then add this fish in the tank builder for the full stocking.
Filtration & heating
A 80L minimum tank needs a filter rated for at least 320L/hr turnover and a heater to hold 22–28°C reliably.
Plant suggestions
Penguin tetra does well in planted tanks. Plants compatible with 22–28°C and pH 5.5–7.5:
Research: partially verified · Confidence: high · 3 linked source(s). We do not invent citations.
How Fishori evaluates compatibility (same logic as pair and tank tools).
- Seriously Fish. Thayeria boehlkei
Primary: aquarium size, water chemistry, behaviour, and compatibility (URL verified in upgrade script; recheck if site content changes).
- FishBase. Thayeria boehlkei
Secondary: taxonomy, distribution, and maximum length in nature; cross-check with aquarium import lines and measured tank parameters.
- Wikipedia. Thayeria boehlkei
Secondary: general species context; verify all husbandry numbers against a dedicated aquarium care sheet and your test kit, not a single table row.
Evidence notes
- The Seriously Fish profile for the binomial in this record was successfully reached as the primary aquarium reference.
- FishBase contributes natural-range size and habitat context. Translate those numbers through your heater, your water report, and your tank footprint before stocking.
- Wikipedia is only cited if the article URL returned OK. Use it for orientation, not as the only care sheet for an import.
- All compatibility text reflects typical hobby experience and the Fishori model. Individual fish, shop stress, and the order tank mates are added in can still defy a single-paragraph label.
Common questions about Penguin tetra
- How big do Penguin tetra get?
- Penguin tetra adults reach about 6 cm. Shop fish look smaller; stock for the adult length.
- What size tank does Penguin tetra need?
- 80L is the planning floor for adult swimming space and bioload. A 98L+ tank is the more comfortable long-term footprint. Length and depth matter as much as raw litres for active or territorial fish.
- Are Penguin tetra aggressive?
- Penguin tetras are peaceful midwater schoolers that look busier than neons because of the wagging swim. They rarely start fights; they create motion that bothers slow, long-finned fish in short tanks. Honest group size turns the motion into a school instead of a panic signal.
- Do Penguin tetra need to be kept in a group?
- Schooling species — buy 6+ together. Smaller groups stress and lose colour.
- What is the most common mistake with Penguin tetra?
- Buying five penguin tetras for a crowded short tank is how the waggling school stresses everyone else. They need a proper group of six or more and lateral space for the swimming pattern that makes them interesting. Under-stocked or under-spaced, they look nervous and push calmer fish into the glass.
- What fish can live with Penguin tetra?
- The Penguin tetra profile lists Boesemani Rainbowfish, Congo Tetra, Dwarf Gourami, Ember Tetra among its safer pairings (engine-checked GOOD). Corydoras Catfish, Pea Puffer, Serpae Tetra, Tiger Barb are conditional (CAUTION): workable only with the specific conditions on each pair page. Avoid African Cichlid, Green Terror, Jack Dempsey, Oscar (RISKY). Run the pair checker for your exact water and tank size before stocking.