Should I buy it?
Red-tailed catfish
Phractocephalus hemioliopterus
Also known as: redtail catfish, rtc
Reaches 120 cm and requires 2000L or more at adult size. Sold as 8 cm juveniles to aquarists who do not understand the commitment.
Red-tailed catfish tank mates · 300L tank size hub
aggressive · advanced care
Sources & confidencehigh · partially verified · beginner: not recommended
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: 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.
Common mistakeBuying a juvenile redtail for a 200L ‘large’ tank expecting it to stay manageable is how keepers invent an un-rehomeable monster. Adults need thousands of litres. Shop cuteness is not a stocking licence — plan the adult or do not buy the juvenile.
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) and a published minimum near **2000L**. Shop tanks are not adult housing.
- Mouth gap vs tiny tank mates. May eat tank mates small enough to fit the adult mouth — plan adult sizes, not shop sizes.
- Specialist husbandry. Red-tailed catfish is fine singly or as a researched pair — check behaviour before doubling up.
More issue cards below, after species context.
Additional planning warnings
Shrimp & snails
Not shrimp-safe — adults, fry, or both get eaten.
What most shops don't tell you
- 1.Myth: juvenile redtail catfish stay manageable in a large home community if they grow up with tank mates. Reality: adults need ~2000L-class systems and eat what fits — ‘they grew up together’ is a schedule, not a law, and rehoming is nearly impossible.
- 2.Predation risk scales with gape, night feeding, and crowding. 'they grew up together' is a schedule, not a law.
- 3.Sold as a 10 cm 'monster plec' in a 200L community. By year three the fish is 60 cm.
- 4.Housed with any tank mate small enough to be food. Adults eat oscars.
- 5.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.
- 6.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
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- 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 listed.
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 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.
Example setups
Starting points only. Run the pair checker for every fish you add.
Avoid “one of everything” baskets — Red-tailed catfish belongs in a plan built around territory, line-of-sight breaks, and matched water chemistry.
Compatibility
Tank mates for Red-tailed catfish
No unconditional “safe” tank mates are listed for Red-tailed catfish — the only curated entries are avoid pairings. Avoid (RISKY): Boesemani Rainbowfish, Chili Rasbora, Corydoras Catfish, Dwarf Gourami, Ember Tetra. 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.
None listed. Use the pair checker before mixing.
Needs planning
Read the blocking rule on each pair page before experimenting.
None listed. Use the pair checker before mixing.
Usually avoid
Do-not-stock combinations on conservative hobby rules.
No safe-mate list on this record yet. Use the fish index to find species with similar care, then run a pair check before you buy.
Behaviour and temperament
Redtail catfish are aggressive predators by size and appetite. They are not community fish at any adult stage. Juveniles look calm beside tetras until the mouth catches up. Stress and damage are inevitable in home community footprints that cannot hold the adult.
What sets them off
- Crowding and limited territory
- Similar-looking fish in the same tank
- Spawning, for any breeding pair
Fin nipping: Not a habitual fin-nipper; stressed or crowded individuals can still test fins.
Predation: May eat tank mates small enough to fit the adult mouth — plan adult sizes, not shop sizes.
Territory: Holds a patch (cave, corner, or surface). Break sight lines so neighbours can pass.
Planted tanks: good — easy plant ideas
In the glass: typical and warning signs
- A giant patrols bottom-to-mid water and treats anything swallowable as food.
- Heavy waste production is normal ownership at adult size — filtration must match.
- Pacing in a few-hundred-litre tank means the footprint failed years before adult length.
- Missing tank mates overnight means predation, not a filter intake mystery.
- Mouth-size predation is ownership math, not a bad apple in the batch.
- They do not ‘settle’ into neon communities as adults — the chart was always wrong.
- Do not buy the juvenile unless the adult system already exists.
- Remove all swallowable fish long before adult size — waiting guarantees disappearances.
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Water, food, and grouping
Hardness
soft
Diet
carnivore
Redtail catfish are enormous carnivores that need serious meaty foods and produce serious waste. A community pellet pinch is not a feeding plan for a fish that can reach metre-class length. Feed by appetite with appropriate large-predator foods only if you already have public-aquarium-scale filtration and volume — not a home 200L kit.
Shrimp & snails
Not shrimp-safe — adults, fry, or both get eaten.
Red-tailed catfish is fine singly or as a researched pair — check behaviour before doubling up.
- 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
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 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:
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. 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.
Common questions about Red-tailed catfish
- How big do Red-tailed catfish get?
- Red-tailed catfish adults run about 100–130 cm. In home tanks they usually land near 120 cm — plan space and filtration for that, not the juvenile in the shop bag.
- What size tank does Red-tailed catfish need?
- 2000L is the planning floor for adult swimming space and bioload. A 3000L+ tank is the more comfortable long-term footprint. Length and depth matter as much as raw litres for active or territorial fish.
- Are Red-tailed catfish aggressive?
- Redtail catfish are aggressive predators by size and appetite. They are not community fish at any adult stage. Juveniles look calm beside tetras until the mouth catches up. Stress and damage are inevitable in home community footprints that cannot hold the adult.
- What is the most common mistake with Red-tailed catfish?
- Buying a juvenile redtail for a 200L ‘large’ tank expecting it to stay manageable is how keepers invent an un-rehomeable monster. Adults need thousands of litres. Shop cuteness is not a stocking licence — plan the adult or do not buy the juvenile.
- What fish can live with Red-tailed catfish?
- This profile currently has no curated unconditional safe-mates shortlist for Red-tailed catfish. Other species may still return GOOD in the pair checker, so check the exact pair rather than treating this shortlist as exhaustive. Avoid Boesemani Rainbowfish, Chili Rasbora, Corydoras Catfish, Dwarf Gourami (RISKY). Run the pair checker for your exact water and tank size before stocking.