Angelfish and Serpae tetra
Can these two share a tank? The assessment below is derived from stored behavioural and environmental traits, not from a compatibility chart.
Should not be attempted. At least one factor is expected to cause harm.
- Minimum volume
- 270 L
- Minimum length
- 130 cm
- Factors considered
- 10
Concerns
Angelfish reaches about 15 cm and takes fish small enough to swallow. At roughly 4 cm, an adult Serpae tetra is inside that range. This is usually discovered as fish quietly disappearing overnight rather than as visible aggression.
Derived from: traits.predation.smallFish, adultSize on both records, and the stored body form and gape of both
Serpae tetra reliably nips trailing fins, and Angelfish carries the kind of fins that get nipped. Damaged fins are also an entry point for secondary infection, so this is a welfare issue rather than a cosmetic one.
Derived from: traits.finNipping and traits.vulnerableFins
Angelfish becomes markedly more aggressive while spawning. A pairing that has been peaceful for months can change within a day, so plan for where the other animal goes if it does.
Derived from: traits.breedingAggression
Serpae tetra is a boisterous, fast-moving fish and Angelfish is a slow, deliberate one. The slower animal typically loses out at feeding time and spends more time hiding, neither of which is obvious from a quick look at the tank.
Derived from: traits.activity on both records
Temperature requirements overlap at 24–27 °C, though the band does not sit centrally for both animals. Aim for the middle of it and keep the heater accurate.
Derived from: environment.temperature on both records
Angelfish defends a territory and both animals use the same part of the tank, so give the territory-holder a defensible area away from the main swimming space.
Derived from: traits.territoriality and zone on both records
Both species occupy the midwater of the tank, so allow for the shared space when judging the footprint.
Derived from: zone and traits.activity on both records
Why it can work
- pH requirements overlap at 6–7.5.
- Hardness requirements overlap at 2–15 °dGH.
- Serpae tetra needs a group of at least 10. Kept in smaller numbers it is not simply lonely — shoaling species held below their threshold show chronic stress behaviour, colour loss and, in several species, increased aggression towards tankmates.
Conditions
Most interesting pairings are conditional on something. These are the things the keeper can actually change.
- At least 10 Serpae tetra, counted as one group
Derived, or documented?
These are different claims and are shown separately. The verdict above is derived from stored traits — arithmetic on AquariumHQ's own records. Whether the pairing is actually reported to work is a separate question, and for most pairs the honest answer is that we hold nothing.
Environmental compatibility
Derived from stored traits
Temperature, pH, hardness, size and behavioural traits compared between the two records. Sound as far as it goes, and it is not evidence that the pairing works.
Behavioural evidence
Widely reported in practice
Reported consistently across aquarium practice without a single citable source. Treated as real but not as measurement.
AquariumHQ's overall position
One of the better-attested bad pairings in the hobby. The damage is not usually fatal and it is chronic, and an angelfish with shredded ventrals in a tank with serpae tetras is not a mystery.
What would change it: A group of ten or more in a long tank reduces it materially. Fewer than six makes it certain.
Factor by factor
- Fin-nippingReported
Serpae tetras are among the most consistently reported fin-nippers in the trade, and an angelfish's trailing ventral filaments are the most exposed fins in a community tank. This combination is reported more often than almost any other nipping pairing.
- Group sizeDerived
Serpae tetras nip more in inadequate groups and redirect within the shoal in adequate ones. The behaviour is reduced by numbers rather than eliminated.
- WaterDerived
Soft, warm, slightly acidic suits both. The pairing fails on behaviour, not chemistry.
| Depends on | How much |
|---|---|
| Tank size and dimensions | significant |
| Life stage | minor |
| The individual animal | significant |
How good is the overlap?
Whether two ranges intersect is a necessary condition, not evidence. What matters is WHERE the shared band sits: an overlap at the top of one animal's range and the bottom of the other's is a forced compromise however wide it looks, and it is the case a simple intersection test cannot see.
| Dimension | Assessment | What that means here |
|---|---|---|
| Temperature | Workable | The shared band 24–27 °C is usable, though it does not sit centrally for both animals. |
| pH | Workable | The shared band 6–7.5 pH is usable, though it does not sit centrally for both animals. |
| Hardness | Comfortable for both | The shared band 2–15 °dGH sits centrally in both ranges, with room to drift. |
Factor by factor
Every factor states what it rests on. Most are derived from the traits stored on both records — sound arithmetic on AquariumHQ's own data, and not a report about how the pairing actually goes. Where a factor says 'not known', the data is missing and saying so matters, because a missing factor and a favourable one look identical once both are absent.
| Factor | Basis | Finding |
|---|---|---|
| Temperature | Derived from stored traits | Workable. The shared band 24–27 °C is usable, though it does not sit centrally for both animals. |
| pH | Derived from stored traits | Workable. The shared band 6–7.5 pH is usable, though it does not sit centrally for both animals. |
| Hardness | Derived from stored traits | Comfortable for both. The shared band 2–15 °dGH sits centrally in both ranges, with room to drift. |
| Body size | Derived from stored traits | Angelfish reaches about 15 cm against 4 cm for Serpae tetra — a ratio of 3.8. Size disparity drives opportunistic predation independently of temperament. |
| Predation | Derived from stored traits | Highest predation risk in either direction is "high". |
| Territoriality | Derived from stored traits | Strongest territoriality across the pair is "moderate". |
| Breeding aggression | Derived from stored traits | Breeding aggression reaches "strong". A pairing peaceful for months can change within a day of a spawn. |
| Fin-nipping | Evidence-backed | One animal nips trailing fins and the other carries the kind of fins that get nipped. Damaged fins are an entry point for secondary infection, so this is a welfare matter rather than a cosmetic one. Reported: Serpae tetras are among the most consistently reported fin-nippers in the trade, and an angelfish's trailing ventral filaments are the most exposed fins in a community tank. This combination is reported more often than almost any other nipping pairing. |
| Aggression | Derived from stored traits | Strongest intraspecific aggression across the pair is "moderate". It bears on the pairing because a fish under pressure from its own kind redirects. |
| Social requirements | Derived from stored traits | Serpae tetra needs at least 10. A shoaling species held below its threshold shows chronic stress and, in several species, increased aggression towards tankmates. |
| Group-size dependency | Derived from stored traits | The outcome depends on group size as much as on the pairing: under-grouped shoalers nip more and hide more. |
| Tank zone | Derived from stored traits | Both occupy the midwater of the tank, so the shared space is under pressure. |
| Activity level | Derived from stored traits | One animal is boisterous and the other sedate. The slower one typically loses out at feeding time and hides more, neither of which is obvious from a quick look at the tank. |
| Food competition | Derived from stored traits | Different feeding strategies, so direct competition is limited. |
| Risk to shrimp and snails | Derived from stored traits | Highest risk either animal poses to dwarf shrimp or snails is "near-certain". |
| Effect on plants | Derived from stored traits | Neither animal damages planting. |
| Tank dimensions | Derived from stored traits | The more demanding of the two needs at least 200 L and 100 cm of length before anything else is in the tank. Volume alone does not describe a home for a fish that swims in straight lines. |
| Life stage | Evidence-backed | Life-stage dependency: minor. See the documented record. |
| Individual variation | Evidence-backed | Individual variation: significant. |
Environmental overlap
| Parameter | Shared range | Reading |
|---|---|---|
| Temperature | 24–27 °C | Aim for the middle of the shared band. |
| pH | 6–7.5 | Stability matters more than the exact figure. |
| Hardness | 2–15 °dGH | Check your source water before committing. |
What this assessment cannot tell you
- Individual temperament varies, particularly in cichlids and in bettas, and can override a favourable verdict for Angelfish or Serpae tetra.
- The assessment is for the pair in isolation. A third species can change the outcome in either direction.
- Both animals are assessed at adult size, not at the size they are sold.
- A verdict is a statement about probability, not a guarantee.
Where the two water bands meet
Derived from the ranges AquariumHQ publishes for each species. The compatibility engine reads the same numbers; this is what they look like drawn on one axis.
Temperature (°C)
Scale: 0 to 36 °C.
pH (pH)
Scale: 4 to 9.5 pH.
Hardness (°dGH)
Scale: 0 to 30 °dGH.
Why the bands sit where they do
The overlap above is arithmetic. This is where the two numbers came from — the kind of water each animal is recorded from, and how much room that leaves.
Both animals come from lowland floodplain, which is why the bands below sit where they do.
Angelfish
Lowland floodplain
40–300 µS/cm · still flow · low oxygen
Serpae tetra
Lowland floodplain
40–300 µS/cm · still flow · low oxygen
- TemperatureAngelfish 24–29°CSerpae tetra 22–27°C
Both inside their range from 24–27°C — 60% of the narrower animal’s range.
A wide window. Both animals are inside their own range across most of it, and the tank can be run without either sitting at an edge.
- pHAngelfish 6–7.5Serpae tetra 5–7.5
Both inside their range from 6–7.5 — 100% of the narrower animal’s range.
A wide window. Both animals are inside their own range across most of it, and the tank can be run without either sitting at an edge.
- General hardnessAngelfish 2–15 dGHSerpae tetra 2–15 dGH
Both inside their range from 2–15 dGH — 100% of the narrower animal’s range.
A wide window. Both animals are inside their own range across most of it, and the tank can be run without either sitting at an edge.
Computed from the ranges AquariumHQ publishes for each species, each of which records what it rests on — a source value, a habitat inference, a physiological requirement or a trade convention. Most are habitat inferences, and the species pages say which.