Generally compatible4 concerns

Bolivian ram and Red swamp crayfish

Can these two share a tank? The assessment below is derived from stored behavioural and environmental traits, not from a compatibility chart.

VerdictGenerally compatiblemoderate confidence

Usually works. Minor points to watch are listed below.

Minimum volume: 150 L
Minimum length: 110 cm
Factors considered: 6

Concerns

minortemperature

Temperature requirements overlap at 22–28 °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

minorterritory

Red swamp crayfish 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

minorbreeding aggression

Bolivian ram 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

minorzone competition

Both species occupy the bottom 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 7–7.8.
Hardness requirements overlap at 6–15 °dGH.

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.

Each dimension assessed for the quality of the overlap, not merely its existence.
Dimension	Assessment	What that means here
Temperature	Workable	The shared band 22–28 °C is usable, though it does not sit centrally for both animals.
pH	Workable	The shared band 7–7.8 pH is usable, though it does not sit centrally for both animals.
Hardness	Workable	The shared band 6–15 °dGH is usable, though it does not sit centrally for both animals.

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.

0 evidence-backed17 derived2 not known

Factor	Basis	Finding
Temperature	Derived from stored traits	Workable. The shared band 22–28 °C is usable, though it does not sit centrally for both animals.
pH	Derived from stored traits	Workable. The shared band 7–7.8 pH is usable, though it does not sit centrally for both animals.
Hardness	Derived from stored traits	Workable. The shared band 6–15 °dGH is usable, though it does not sit centrally for both animals.
Body size	Derived from stored traits	Adult sizes are comparable at about 9 cm and 15 cm, so neither is a mouthful for the other.
Predation	Derived from stored traits	Highest predation risk in either direction is "high".
Territoriality	Derived from stored traits	Strongest territoriality across the pair is "strong".
Breeding aggression	Derived from stored traits	Breeding aggression reaches "moderate". 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	Both occupy the bottom of the tank, so the shared space is under pressure.
Activity level	Derived from stored traits	Activity levels are compatible.
Food competition	Derived from stored traits	Both are omnivores feeding in the same part of the tank.
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	Red swamp crayfish eats plants, which constrains the aquascape rather than the pairing.
Tank dimensions	Derived from stored traits	The more demanding of the two needs at least 110 L and 80 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	22–28 °C	Aim for the middle of the shared band.
pH	7–7.8	Stability matters more than the exact figure.
Hardness	6–15 °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 Bolivian ram or Red swamp crayfish.
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.

The two species

Bolivian ramMikrogeophagus altispinosusLarger, plainer and vastly more forgiving than the German blue ram — tolerant of ordinary temperatures and ordinary tap water, and long-lived with it. The dwarf cichlid to start with.Red swamp crayfishProcambarus clarkiiOne of the most damaging freshwater invasive species in the world, farmed for food, sold as an aquarium animal, and named individually on the EU list of invasive alien species of Union concern. It burrows through banks, eats everything, and carries the crayfish plague that has removed native European crayfish from whole river systems.