Angelfish and Zebra danio
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
- 9
Concerns
The shared band 24–25 °C sits at the bottom of one animal's range and the top of the other's. Both would be kept at their limits to accommodate the other. Both animals would be kept at the edge of their ranges to accommodate the other. Nothing here is a recommendation; it is the arithmetic of two incompatible requirements meeting at a point.
Derived from: environment.temperature range position on both records
Angelfish reaches about 15 cm and takes fish small enough to swallow. At roughly 5 cm, an adult Zebra danio is inside that range. This is usually discovered as fish quietly disappearing overnight rather than as visible aggression.
Derived from: traits.predation.smallFish and adultSize on both records
Zebra danio may nip 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
Zebra danio 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
Why it can work
- pH requirements overlap at 6–7.5.
- Hardness requirements overlap at 2–15 °dGH.
- Zebra danio needs a group of at least 8. 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.
- The two occupy different levels of the tank, which reduces direct competition for space.
Conditions
Most interesting pairings are conditional on something. These are the things the keeper can actually change.
- Keep Zebra danio in a group of at least 8 — nipping increases sharply in under-sized groups
- At least 8 Zebra danio, 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
No behavioural evidence held
AquariumHQ holds no behavioural evidence for this pairing. The verdict is derived entirely from stored traits — it is arithmetic on our own records, not a report about how the pairing actually goes.
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 | Forced compromise — neither animal is where it wants to be | The shared band 24–25 °C sits at the bottom of one animal's range and the top of the other's. Both would be kept at their limits to accommodate the other. |
| pH | Comfortable for both | The shared band 6–7.5 pH sits centrally in both ranges, with room to drift. |
| Hardness | Comfortable for both | The shared band 2–15 °dGH sits centrally in both ranges, with room to drift. |
Forced compromise — neither animal is where it wants to be
Both animals would be kept at the edge of their ranges to accommodate the other. Nothing here is a recommendation; it is the arithmetic of two incompatible requirements meeting at a point.
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 | Forced compromise — neither animal is where it wants to be. The shared band 24–25 °C sits at the bottom of one animal's range and the top of the other's. Both would be kept at their limits to accommodate the other. |
| pH | Derived from stored traits | Comfortable for both. The shared band 6–7.5 pH sits centrally in both ranges, with room to drift. |
| 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 5 cm for Zebra danio — a ratio of 3.0. 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 | Derived from stored traits | 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. |
| 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 | Zebra danio needs at least 8. 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 | The two use different levels of the tank, which reduces direct competition for space. |
| 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 | Not known | AquariumHQ holds no record of whether this pairing changes as either animal matures. Stored traits describe adults, so a pairing that fails at adult size looks identical to one that never fails. |
| Individual variation | Not known | AquariumHQ holds no record of how much this pairing varies between individuals. For several species — bettas and cichlids especially — that variation decides the outcome and a species-level verdict cannot express it. |
Environmental overlap
| Parameter | Shared range | Reading |
|---|---|---|
| Temperature | 24–25 °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 Zebra danio.
- 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.