Can Ajamaru Rainbowfish and Dusky Millions Fish Live Together?

Possible with Caution

Keeping Ajamaru 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

Ajamaru Rainbowfish

Melanotaenia ajamaruensis

Dusky Millions Fish

Phalloceros caudimaculatus

🐠Family Group
Ajamaru Rainbowfish
Rainbowfish
Dusky Millions Fish
Livebearers
Temperament
Ajamaru Rainbowfish
Peaceful (2/10)
Dusky Millions Fish
Peaceful (2/10)
Temperature
✓ Compatible
Ajamaru Rainbowfish
24–28°C
Dusky Millions Fish
16–24°C
pH Range
✓ Compatible
Ajamaru Rainbowfish
7.2–8.5
Dusky Millions Fish
7–8
Hardness (dGH)
✓ Compatible
Ajamaru Rainbowfish
8–20
Dusky Millions Fish
8–20
Water Type
✓ Compatible
Ajamaru Rainbowfish
Freshwater Only
Dusky Millions Fish
Brackish Tolerant
Flow Preference
✓ Compatible
Ajamaru Rainbowfish
Moderate
Dusky Millions Fish
Low
Min Tank Volume
Combined: 150 L
Ajamaru Rainbowfish
150 L
Dusky Millions Fish
40 L
Swimming Level
Shared: 2 zones
Ajamaru Rainbowfish
TopMiddle
Dusky Millions Fish
TopMiddle
🏷️Behavior Tags
Ajamaru Rainbowfish
Hyperactive / Fast SwimmerJumper (Lid Required)Fry Predator
Dusky Millions Fish
Hyperactive / Fast SwimmerPlant DestroyerFin Nipper
Stocking calculator

Can your tank handle Ajamaru 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.

Ajamaru Rainbowfish
Dusky Millions Fish
Test both in my tank

Behaviour & Temperament

Both Ajamaru 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.

Ajamaru 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: Ajamaru 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 7.2 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 8–20 dGH. Regular testing will ensure conditions stay within this range.

Tank Setup

To house Ajamaru Rainbowfish and Dusky Millions Fish 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.

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 - 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 Ajamaru 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 Ajamaru Rainbowfish and Dusky Millions Fish.

Show 9 more tank sizes

Frequently Asked Questions

Can Ajamaru 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 Ajamaru Rainbowfish and Dusky Millions Fish 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 Ajamaru 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 Ajamaru Rainbowfish or Dusky Millions Fish aggressive?

Ajamaru 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 Ajamaru Rainbowfish and Dusky Millions Fish need?

Both species overlap in the 7.2–8 pH range. Consistency is key — avoid sudden swings, and test regularly to stay within this window.

Will Dusky Millions Fish nip Ajamaru Rainbowfish's fins?

Dusky Millions Fish is a known fin nipper. If Ajamaru 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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