Siamese fighting fish and Mystery snail
Can these two share a tank? The assessment below is derived from stored behavioural and environmental traits, not from a compatibility chart.
Workable only in unusual circumstances. Not a pairing to plan around.
- Minimum volume
- 55 L
- Minimum length
- 75 cm
- Factors considered
- 7
Concerns
pH ranges overlap only across 7–7.5, which is tighter than most tap-water supplies hold naturally.
Derived from: environment.ph overlap width
Siamese fighting fish harasses slow-moving or long-finned tankmates, and Mystery snail fits that description. Persistent harassment shows up as hiding, clamped fins and refusal to feed long before it shows up as injury.
Derived from: traits.predation.harassment and traits on the second record
Siamese fighting fish 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
Temperature requirements overlap at 24–28 °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
Siamese fighting fish 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
Why it can work
- Hardness requirements overlap at 8–15 °dGH.
- 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.
- At least 55 L with a footprint of 75 cm or more, before counting anything else in the tank
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
Commonly kept and usually survivable, with two separate problems that get blamed on each other. Antenna damage is behavioural and individual; a pitted, thinning shell is chemical and inevitable in betta-soft water. Only the first is about the betta.
What would change it: Harder water helps the snail and costs the betta little. A betta that persistently strips antennae will keep doing it.
Factor by factor
- Antenna nippingReported
Reported consistently and specifically: bettas nip the long antennae of Pomacea, which the snail withdraws and regrows. It is not usually fatal and it is not nothing, and it happens with some individuals and not others.
- Shell hardness requirementDerived
An apple snail is a large calcifier and needs more hardness than a nerite does. A betta's band is softer still, and this pairing puts the snail further outside its requirement than the nerite pairing does.
- Surface competitionDerived
Both breathe air at the surface. The snail extends a siphon and the betta takes gulps, and neither prevents the other.
| Depends on | How much |
|---|---|
| Tank size and dimensions | minor |
| Life stage | none |
| 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 24–28 °C is usable, though it does not sit centrally for both animals. |
| pH | Forced compromise — neither animal is where it wants to be | The shared band 7–7.5 pH sits at the top of one animal's range and the bottom of the other's. Both would be kept at their limits to accommodate the other. |
| Hardness | Workable | The shared band 8–15 °dGH is usable, though it does not sit centrally for both animals. |
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 | Workable. The shared band 24–28 °C is usable, though it does not sit centrally for both animals. |
| pH | Derived from stored traits | Forced compromise — neither animal is where it wants to be. The shared band 7–7.5 pH sits at the top of one animal's range and the bottom of the other's. Both would be kept at their limits to accommodate the other. |
| Hardness | Derived from stored traits | Workable. The shared band 8–15 °dGH is usable, though it does not sit centrally for both animals. |
| Body size | Derived from stored traits | Adult sizes are comparable at about 7 cm and 6 cm, so neither is a mouthful for the other. |
| Predation | Derived from stored traits | Highest predation risk in either direction is "none". |
| 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 | No nipper-and-target combination between these two. |
| Aggression | Derived from stored traits | Strongest intraspecific aggression across the pair is "strong". It bears on the pairing because a fish under pressure from its own kind redirects. |
| Social requirements | Derived from stored traits | Neither animal requires a group. |
| Group-size dependency | Derived from stored traits | The outcome does not depend on group size for either animal. |
| 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 | Activity levels are compatible. |
| 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 "high". |
| 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 40 L and 45 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: none. See the documented record. |
| Individual variation | Evidence-backed | Individual variation: significant. |
Environmental overlap
| Parameter | Shared range | Reading |
|---|---|---|
| Temperature | 24–28 °C | Aim for the middle of the shared band. |
| pH | 7–7.5 | Stability matters more than the exact figure. |
| Hardness | 8–15 °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 Siamese fighting fish or Mystery snail.
- 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.
These two animals come from different kinds of water, and that is where the arithmetic below comes from rather than from anything about their temperaments.
Siamese fighting fish
Rice paddy, ditch and drain
central Thai floodplain and paddy
80–500 µS/cm · still flow · low oxygen
Mystery snail
Lowland floodplain
40–300 µS/cm · still flow · low oxygen
- TemperatureSiamese fighting fish 24–28°CMystery snail 20–28°C
Both inside their range from 24–28°C — 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.
- pHSiamese fighting fish 6–7.5Mystery snail 7–8.5
Both inside their range from 7–7.5 — 33% of the narrower animal’s range.
A real window, and a narrow one. The tank has to be held inside it, and there is little room for the drift that happens between water changes.
- General hardnessSiamese fighting fish 2–15 dGHMystery snail 8–20 dGH
Both inside their range from 8–15 dGH — 58% of the narrower animal’s range.
A real window, and a narrow one. The tank has to be held inside it, and there is little room for the drift that happens between water changes.
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.