Should I buy it?
Red-tailed catfish
Phractocephalus hemioliopterus
Also known as: redtail catfish, rtc, RTC
Fishori provides conservative planning guidance, not guarantees.
Based on multiple reputable aquarium care sources with strong agreement. Use the numbers here as planning defaults — your room, water, and routine still shape real-world outcomes.
Reaches 120 cm and requires 2000L or more at adult size. Sold as 8 cm juveniles to aquarists who do not understand the commitment.
Best for
Specialist large-predator setups with the facilities to house a 120 cm adult. Not suitable for home aquariums by any practical standard.
Avoid if
You have a standard home aquarium. This is a public aquarium or specialist extreme keeper fish.
Top things that go wrong
- Grows large or needs a very big footprint. Red-tailed catfish is often sold at sizes that hide adult length (~120cm on file) and a published minimum near **2000L**. Shop tanks are not adult housing.
- Mouth gap vs tiny tank mates. Predation risk toward smaller tank mates. The figure that matters is the adult mouth size against the adult prey length, not the juvenile sizes in the shop.
- Specialist husbandry. Kept singly or as a paired setup. Check the species profile before doubling up in one tank.
More issue cards below, after species context.
Common mistakeBuying a juvenile redtail catfish for a 200L 'large' tank expecting it to stay manageable. Adults are virtually impossible to rehome.
Additional planning warnings
Shrimp & snails
Shrimp: not safe. The fish will eat adult shrimp, shrimp fry, or both, depending on the size of the shrimp.
What most shops don't tell you
- 1.Predation risk scales with gape, night feeding, and crowding. 'they grew up together' is a schedule, not a law.
- 2.Sold as a 10 cm 'monster plec' in a 200L community. By year three the fish is 60 cm.
- 3.Housed with any tank mate small enough to be food. Adults eat oscars.
- 4.If you are not building a 2-metre class system on purpose, do not buy. Public aquaria are full of rehomed redtails and most cannot take more. Never release to local waters.
- 5.Advanced species — research stable parameters before buying.
About this species
Sold as a 10 cm patterned cute fish, grows to 100 to 130 cm in five to seven years. The shop never mentions the 2000L+ pond-class system the adult needs. Predatory South American giant; a public-aquarium animal in anything but a brief juvenile grow-out tank.
- Pictus catfish250L min · same fish family
- Cuckoo / petricola catfish200L min · same fish family
- Twig / whiptail catfish150L min · same fish family
- Emerald catfish (Brochis)120L min · same fish family
- Bronze corydoras100L min · same fish family
- Sterba's Corydoras100L min · same fish family
- Upside-down Catfish100L min · same fish family
- Adolfoi cory80L min · same fish family
No close matches on file.
No reverse lookups on file yet.
Plan grid
Key limits are shown above; this section adds planning detail: pH band, swim level, bioload and activity, and the radar.
Swim zones
Planning trait chart
Six indices for comparing species on paper before you spend.
- Beginner ease6
- Peacefulness0
- Community fit0
- Small-tank fit0
- Hardiness36
- Energy86
Numbers are deterministic planning indices from Fishori fields — not a scientific score of your individual fish.
Common setup sketches
Conservative patterns from Fishori fields — still run the pair checker for every species you add; sketches are not a stocking guarantee.
Avoid “one of everything” baskets — Red-tailed catfish belongs in a plan built around territory, line-of-sight breaks, and matched water chemistry.
Tank mate intelligence
Use the "Often compatible" lists as a shortlist, not a stocking plan. Always run the pair tool and check the footprint of your actual tank first. Verify behaviour for Red-tailed catfish against your own reading before you buy.
Pair-level compatibility with this fish as anchor.
Read the blocking rule on each pair page before experimenting.
Do-not-stock combinations on conservative hobby rules.
Compare with
Run a real pair check: Red-tailed catfish + Oscar
- Try Oscar — open the pair check.
- Try Bala / silver shark — open the pair check.
- Try Giant danio — open the pair check.
- Try Tinfoil barb — open the pair check.
Behaviour, temperament, and what to watch
Prose and lists come from the same record: read temperament first, then glass-level signals so you are not surprised after day three.
Red-tailed catfish is aggressive in mixed company. Treats any fish small enough to fit in its mouth as food. Mouth size at adult length matters, not the prey's listed adult size. Holds territory on substrate, in caves, or at the surface film. Break the sight lines with hardscape to keep the resident off the visitor.
Stress / aggression triggers on file
- Crowding and limited territory
- Similar-looking fish in the same tank
- Spawning, for any breeding pair
Fin nipping: Not a habitual fin-nipper, but individuals can still test fins under stress or in a crowded tank.
Predation: Predation risk toward smaller tank mates. The figure that matters is the adult mouth size against the adult prey length, not the juvenile sizes in the shop.
Territory: Holds territory on substrate, in caves, or at the surface film. Break the line of sight with hardscape, and avoid placing the tank where the fish can see its own reflection.
Planted tanks: good — easy plant ideas
In the glass: typical and warning signs
- Busy at feeding time — expects food to hit the water predictably.
- Clamped fins, gasping at the surface, hiding non-stop, or refusing food after the first week.
- Rapid breathing when parameters swing — fix ammonia/nitrite first, then reassess mates.
- Chasing one individual repeatedly, torn fins on tank mates, or food theft every feed.
- Corner guarding, flaring, or body-blocking — territory is normal until it becomes relentless.
- Separate or rehome if injuries appear, one fish is pinned, or feeding becomes a daily chase.
- If water is stable but behaviour worsens, reduce stocking or remove the highest-impact species first.
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Care parameters: water, food, inverts, grouping
Chemistry and group rules sit here so you are not re-reading the same line from tank mate or temperament blocks. Swim level is in the plan grid above.
Hardness
soft
Diet
carnivore
Small invertebrates, frozen bloodworm or daphnia, and protein-rich prepared foods. Rotate the menu and feed by appetite rather than by clock.
Shrimp & snails
Shrimp: not safe. The fish will eat adult shrimp, shrimp fry, or both, depending on the size of the shrimp.
Kept singly or as a paired setup. Check the species profile before doubling up in one tank.
Breeding behaviour depends on the species. Research before you buy a mixed-sex group of this fish.
- Hold 24 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.
- Footprint: short wide tanks and tall narrow tanks fish differently for the same volume. Match the tank shape to the swim pattern, not just the litre count.
- Tank volume meets or exceeds 2000L published minimum for adults.
- Heater can hold 24–28°C without cooking cooler-water tank mates.
- No known fin-nippers paired with long-finned fish unless you accept documented risk.
- No tank mates small enough to fit the adult mouth gap for this species.
- Filter maturity / stable parameters before adding sensitive stock.
Explore and stocking hubs
Same library as the rest of Fishori: tank-mate index for this species, category peers, guides, and litre-based stocking lists where min tank on file is within the hub volume.
Plan with tools
Pair-level rules and multi-fish stocking use the same conservative engine — add this fish in the tank builder only after mates pass pair checks.
Filtration & heating
A 2000L minimum tank needs a filter rated for at least 8000L/hr turnover and a heater to hold 24–28°C reliably.
Plant suggestions
Red-tailed catfish does well in planted tanks. Plants compatible with 24–28°C and pH 5.5–7.5:
Profile status: partially verified · Evidence tier: high · 3 linked source(s). Fishori does not fabricate citations.
Fishori uses conservative planning rules based on these sources.
Confidence is explained in the summary at the top of this page (same tier as here), not repeated below.
How Fishori evaluates compatibility (same logic as pair and tank tools).
- Seriously Fish. Phractocephalus hemioliopterus
Primary: aquarium size, water chemistry, behaviour, and compatibility (URL verified in upgrade script; recheck if site content changes).
- FishBase. Phractocephalus hemioliopterus
Secondary: taxonomy, distribution, and maximum length in nature; cross-check with aquarium import lines and measured tank parameters.
- Wikipedia. Phractocephalus hemioliopterus
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.
- Fishori profiles work from typical aquarium trade sizes and hobby care norms. Specialist site checks and literature review for this species are not yet recorded here, so the ranges on this page are planning numbers rather than guarantees.