Can Allen's Rainbowfish and Dusky Millions Fish Live Together?
Keeping Allen's Rainbowfish and Dusky Millions Fish together is possible but requires caution, though some care is needed. Provide a spacious tank of at least 150 litres with plenty of hiding spots to reduce stress. Monitor behaviour closely, especially during the first few weeks.
At a Glance
Can your tank handle Allen's Rainbowfish and Dusky Millions Fish?
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.
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Behaviour & Temperament
Both Allen's Rainbowfish and Dusky Millions Fish are peaceful species with an aggression score of 2/10. Their matching temperaments mean neither fish is likely to dominate the other in a shared aquarium.
Allen's Rainbowfish and Dusky Millions Fish 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.
Worth noting: Allen's Rainbowfish is a known jumper, so a tight-fitting lid is essential.
To improve the chances of a peaceful coexistence in this community tank: Keep fin nippers in larger groups to distribute nipping behaviour among conspecifics rather than tank mates.
Water Parameters
The safe temperature window for both species falls between 24°C and 24°C. Aim for the midpoint of this range (around 24.0°C) for optimal comfort.
Both fish can tolerate a pH between 7 and 8. Maintaining a stable value within this band is more important than hitting an exact number.
For general hardness, the shared comfort zone is 8–15 dGH. Regular testing will ensure conditions stay within this range.
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Tank Setup
To house Allen's Rainbowfish and Dusky Millions Fish together, plan for an aquarium of at least 150 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.
Because this pairing requires extra vigilance, include plenty of hiding spots — caves, driftwood, and dense plant clusters — so the less dominant fish can retreat when needed.
Specific environmental needs for this combination include: Plants - lighly covered, Driftwood (Digestion/Hiding), Plants - Densely covered, Plants - Floating, Established Algae (Otocinclus). Meeting these requirements will help both species thrive.
Note a potential conflict in setup requirements: Dusky Millions Fish is a plant destroyer, which conflicts with Allen's Rainbowfish's requirement for live plants. Compromise where possible or prioritise the more critical need.
Both species do well with moderate (standard) water movement, so a standard filtration setup rated for the tank volume should suffice.
Suitable Tank Sizes
Standard aquarium sizes large enough for both Allen's Rainbowfish and Dusky Millions Fish.
55 Gallon Standard
60 Gallon Breeder
75 Gallon Standard
90 Gallon Standard
125 Gallon Standard
150 Gallon High
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Frequently Asked Questions
Can Allen's Rainbowfish and Dusky Millions Fish live together?
They can coexist, but the pairing requires careful monitoring. Provide ample space (at least 150 litres), plenty of hiding spots, and watch for signs of stress or aggression.
What size tank do Allen's Rainbowfish and Dusky Millions Fish need?
A minimum of 150 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 Allen's Rainbowfish and Dusky Millions Fish together?
Keep the aquarium between 24°C and 24°C. A target of around 24.0°C sits comfortably within both species' preferred ranges.
Are Allen's Rainbowfish or Dusky Millions Fish aggressive?
Allen's Rainbowfish is peaceful (2/10) and Dusky Millions Fish is peaceful (2/10). Their similar temperaments generally lead to a peaceful coexistence.
What pH do Allen's Rainbowfish and Dusky Millions Fish need?
Both species overlap in the 7–8 pH range. Consistency is key — avoid sudden swings, and test regularly to stay within this window.
Will Dusky Millions Fish nip Allen's Rainbowfish's fins?
Dusky Millions Fish is a known fin nipper. If Allen's Rainbowfish has long or flowing fins, there is a real risk of fin damage. Keeping Dusky Millions Fish in a larger group can help redirect nipping behaviour toward conspecifics.
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