Can Betta Macrostoma and Crimsonspotted Rainbowfish Live Together?
Betta Macrostoma and Crimsonspotted Rainbowfish are not recommended as tank mates due to conflicting pH requirements and incompatible hardness ranges. 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 Betta Macrostoma and Crimsonspotted Rainbowfish?
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
Betta Macrostoma is a moderately assertive species (6/10), while Crimsonspotted Rainbowfish is peaceful (2/10). This notable difference means Betta Macrostoma may occasionally assert dominance over Crimsonspotted Rainbowfish.
Betta Macrostoma and Crimsonspotted Rainbowfish both frequent the Top (Surface) and Middle (Open Water) region of the setup. This overlap can increase competition for space, so providing ample room and cover is important to keep both species comfortable.
Additional behavioural considerations to keep in mind: Hyperactive swimmers can stress shy, slow-moving species through constant motion.
Worth noting: Betta Macrostoma is a known jumper, so a tight-fitting lid is essential.
Water Parameters
The safe temperature window for both species falls between 20°C and 25°C. Aim for the midpoint of this range (around 22.5°C) for optimal comfort.
The pH requirements of Betta Macrostoma (4–6) and Crimsonspotted Rainbowfish (6.5–8) do not overlap, making it impossible to satisfy both species simultaneously.
Hardness requirements are incompatible: Betta Macrostoma needs 0–5 dGH while Crimsonspotted Rainbowfish requires 8–20 dGH.
Tank Setup
To house Betta Macrostoma and Crimsonspotted Rainbowfish together, plan for an aquarium of at least 150 litres with a minimum length of 90 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: Leaf Litter/Blackwater, Driftwood (Digestion/Hiding), Plants - Floating, Plants - Densely covered. Meeting these requirements will help both species thrive.
Both species do well with low (still water) water movement, so a standard filtration setup rated for the tank volume should suffice.
Why This Pairing Usually Fails in Practice
Betta Macrostoma and Crimsonspotted Rainbowfish 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 Betta Macrostoma and Crimsonspotted Rainbowfish.
40 Gallon Breeder
55 Gallon Standard
60 Gallon Breeder
75 Gallon Standard
90 Gallon Standard
125 Gallon Standard
Show 9 more tank sizes
Frequently Asked Questions
Can Betta Macrostoma and Crimsonspotted Rainbowfish live together?
No. This combination is not recommended. Key incompatibilities — such as critical behavioural conflicts — make cohabitation unsafe.
What size tank do Betta Macrostoma and Crimsonspotted Rainbowfish need?
A minimum of 150 litres (tank length at least 90 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 Betta Macrostoma and Crimsonspotted Rainbowfish together?
Keep the aquarium between 20°C and 25°C. A target of around 22.5°C sits comfortably within both species' preferred ranges.
Are Betta Macrostoma or Crimsonspotted Rainbowfish aggressive?
Betta Macrostoma is moderately assertive (6/10) and Crimsonspotted Rainbowfish is peaceful (2/10). The gap in aggression levels means the calmer fish may experience stress from the more assertive one.
What pH do Betta Macrostoma and Crimsonspotted Rainbowfish need?
Their pH requirements do not overlap. Betta Macrostoma prefers 4–6, while Crimsonspotted Rainbowfish needs 6.5–8. This makes them incompatible in the same water chemistry.
How do I manage Betta Macrostoma's territorial behaviour?
Provide line-of-sight breaks using rocks, driftwood, and dense planting. A larger tank gives Betta Macrostoma 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.
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Guidarium Editorial Desk
Reviewed against Guidarium care, stocking, and compatibility standards. Read the editorial policy.
- Last reviewed
- May 4, 2026
- Last updated
- May 4, 2026
- Issues or corrections?
- Contact the editorial team
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