Can Altum Angel and Northern Mountain Swordtail Live Together?
Altum Angel and Northern Mountain Swordtail are not recommended as tank mates due to no temperature overlap and 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 Altum Angel and Northern Mountain Swordtail?
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
Altum Angel is a moderately assertive species (5/10), while Northern Mountain Swordtail is generally mild-mannered (3/10). This modest difference means Altum Angel may occasionally assert dominance over Northern Mountain Swordtail.
Altum Angel and Northern Mountain Swordtail both frequent the 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: Northern Mountain Swordtail is a known jumper, so a tight-fitting lid is essential.
Water Parameters
There is no temperature overlap between Altum Angel (27–32°C) and Northern Mountain Swordtail (20–25°C). This fundamental mismatch makes long-term cohabitation impractical.
The pH requirements of Altum Angel (4.5–6.5) and Northern Mountain Swordtail (7–8) do not overlap, making it impossible to satisfy both species simultaneously.
Hardness requirements are incompatible: Altum Angel needs 1–5 dGH while Northern Mountain Swordtail requires 8–20 dGH.
Tank Setup
To house Altum Angel and Northern Mountain Swordtail together, plan for an aquarium of at least 400 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: Sand (Sifters), Driftwood (Digestion/Hiding), Leaf Litter/Blackwater, Plants - Floating, Plants - Densely covered. Meeting these requirements will help both species thrive.
Altum Angel prefers Low (Still Water) flow while Northern Mountain Swordtail needs High (River/Stream) flow. Consider positioning filter outlets and using baffles to create zones of different current intensity within the same tank.
Why This Pairing Usually Fails in Practice
Altum Angel and Northern Mountain Swordtail 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 Altum Angel and Northern Mountain Swordtail.
Frequently Asked Questions
Can Altum Angel and Northern Mountain Swordtail live together?
No. This combination is not recommended. Key incompatibilities — such as non-overlapping temperature ranges — make cohabitation unsafe.
What size tank do Altum Angel and Northern Mountain Swordtail need?
A minimum of 400 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 Altum Angel and Northern Mountain Swordtail together?
Unfortunately, there is no temperature range that satisfies both species. Altum Angel requires 27–32°C, while Northern Mountain Swordtail needs 20–25°C.
Are Altum Angel or Northern Mountain Swordtail aggressive?
Altum Angel is moderately assertive (5/10) and Northern Mountain Swordtail is generally mild-mannered (3/10). Their similar temperaments generally lead to a peaceful coexistence.
What pH do Altum Angel and Northern Mountain Swordtail need?
Their pH requirements do not overlap. Altum Angel prefers 4.5–6.5, while Northern Mountain Swordtail needs 7–8. This makes them incompatible in the same water chemistry.
How do I manage Altum Angel's territorial behaviour?
Provide line-of-sight breaks using rocks, driftwood, and dense planting. A larger tank gives Altum Angel 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 7, 2026
- Last updated
- May 7, 2026
- Issues or corrections?
- Contact the editorial team
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