Can Cairns Rainbowfish and Pseudotropheus Acei Live Together?
Cairns Rainbowfish and Pseudotropheus Acei are not recommended as tank mates due to conflicting pH requirements. Housing these species together is likely to result in stress, health problems, or direct harm to one or both fish.
At a Glance
Can your tank handle Cairns Rainbowfish and Pseudotropheus Acei?
Compatibility is only part of the answer. Test both fish with your real tank size, current stock, and maintenance needs to see if you have enough space and a safe stocking level before you add them.
Behaviour & Temperament
Cairns Rainbowfish is a peaceful species (2/10), while Pseudotropheus Acei is generally mild-mannered (4/10). This modest difference means Pseudotropheus Acei may occasionally assert dominance over Cairns Rainbowfish.
Cairns Rainbowfish and Pseudotropheus Acei both frequent the Middle (Open Water) and Top (Surface) region of the setup. This overlap can increase competition for space, so providing ample room and cover is important to keep both species comfortable.
Worth noting: Cairns Rainbowfish is a known jumper, so a tight-fitting lid is essential.
Water Parameters
The safe temperature window for both species falls between 24°C and 26°C. Aim for the midpoint of this range (around 25.0°C) for optimal comfort.
The pH requirements of Cairns Rainbowfish (6.5–7.6) and Pseudotropheus Acei (7.8–8.6) do not overlap, making it impossible to satisfy both species simultaneously.
For general hardness, the shared comfort zone is 10–10 dGH. Regular testing will ensure conditions stay within this range.
Tank Setup
To house Cairns Rainbowfish and Pseudotropheus Acei together, plan for an aquarium of at least 200 litres with a minimum length of 120 cm. This recommendation combines the stricter species minimums with a community-load allowance so the pairing has realistic long-term space and filtration headroom.
Providing a mix of open swimming space and sheltered areas with rocks, driftwood, or plants will keep both species comfortable and allow natural behaviour.
Specific environmental needs for this combination include: Smooth Gravel (Sensitive Barbels), Driftwood (Digestion/Hiding), Leaf Litter/Blackwater, Sand (Sifters). Meeting these requirements will help both species thrive.
Both species do well with high (river/stream) water movement, so a standard filtration setup rated for the tank volume should suffice.
Why This Pairing Usually Fails in Practice
Cairns Rainbowfish and Pseudotropheus Acei are the kind of pair that can look acceptable in a shop but become a maintenance problem at home. The main risk is not a single number in the chart; it is the way incompatible behavior, water needs, or pressure on space compounds over time once both fish are established in the same tank.
Suitable Tank Sizes
Standard aquarium sizes large enough for both Cairns Rainbowfish and Pseudotropheus Acei.
55 Gallon Standard
60 Gallon Breeder
75 Gallon Standard
90 Gallon Standard
125 Gallon Standard
150 Gallon High
Frequently Asked Questions
Can Cairns Rainbowfish and Pseudotropheus Acei live together?
No. This combination is not recommended. Key incompatibilities — such as critical behavioural conflicts — make cohabitation unsafe.
What size tank do Cairns Rainbowfish and Pseudotropheus Acei need?
A minimum of 200 litres (tank length at least 120 cm) is recommended. This provides enough space for both species to establish their own areas and reduces the likelihood of territorial disputes.
What water temperature is best for Cairns Rainbowfish and Pseudotropheus Acei together?
Keep the aquarium between 24°C and 26°C. A target of around 25.0°C sits comfortably within both species' preferred ranges.
Are Cairns Rainbowfish or Pseudotropheus Acei aggressive?
Cairns Rainbowfish is peaceful (2/10) and Pseudotropheus Acei is generally mild-mannered (4/10). Their similar temperaments generally lead to a peaceful coexistence.
What pH do Cairns Rainbowfish and Pseudotropheus Acei need?
Their pH requirements do not overlap. Cairns Rainbowfish prefers 6.5–7.6, while Pseudotropheus Acei needs 7.8–8.6. This makes them incompatible in the same water chemistry.
How do I manage Pseudotropheus Acei's territorial behaviour?
Provide line-of-sight breaks using rocks, driftwood, and dense planting. A larger tank gives Pseudotropheus Acei space to claim a territory without encroaching on the other fish's area. Adding décor that divides the tank into distinct zones works especially well.
Shared setup supplies
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Guidarium Editorial Desk
Reviewed against Guidarium care, stocking, and compatibility standards. Read the editorial policy.
- Last reviewed
- May 7, 2026
- Last updated
- May 7, 2026
- Issues or corrections?
- Contact the editorial team
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