Can Electric Blue Johannii and Festivum Live Together?
Electric Blue Johannii and Festivum 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 Electric Blue Johannii and Festivum?
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
Electric Blue Johannii is a semi-aggressive species (8/10), while Festivum is generally mild-mannered (4/10). This notable difference means Electric Blue Johannii may occasionally assert dominance over Festivum.
Electric Blue Johannii and Festivum 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: Two territorial species may clash over territory, especially in smaller tanks.
Worth noting: Festivum 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 28°C. Aim for the midpoint of this range (around 26.0°C) for optimal comfort.
The pH requirements of Electric Blue Johannii (7.8–8.6) and Festivum (5.5–7.2) do not overlap, making it impossible to satisfy both species simultaneously.
For general hardness, the shared comfort zone is 10–12 dGH. Regular testing will ensure conditions stay within this range.
Tank Setup
To house Electric Blue Johannii and Festivum together, plan for an aquarium of at least 226 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: Sand (Sifters), Established Algae (Otocinclus), Driftwood (Digestion/Hiding), Plants - Floating. Meeting these requirements will help both species thrive.
Both species do well with moderate (standard) water movement, so a standard filtration setup rated for the tank volume should suffice.
Why This Pairing Usually Fails in Practice
Electric Blue Johannii and Festivum 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 Electric Blue Johannii and Festivum.
60 Gallon Breeder
75 Gallon Standard
90 Gallon Standard
125 Gallon Standard
150 Gallon High
180 Gallon Standard
Frequently Asked Questions
Can Electric Blue Johannii and Festivum live together?
No. This combination is not recommended. Key incompatibilities — such as critical behavioural conflicts — make cohabitation unsafe.
What size tank do Electric Blue Johannii and Festivum need?
A minimum of 226 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 Electric Blue Johannii and Festivum together?
Keep the aquarium between 24°C and 28°C. A target of around 26.0°C sits comfortably within both species' preferred ranges.
Are Electric Blue Johannii or Festivum aggressive?
Electric Blue Johannii is semi-aggressive (8/10) and Festivum is generally mild-mannered (4/10). The gap in aggression levels means the calmer fish may experience stress from the more assertive one.
What pH do Electric Blue Johannii and Festivum need?
Their pH requirements do not overlap. Electric Blue Johannii prefers 7.8–8.6, while Festivum needs 5.5–7.2. This makes them incompatible in the same water chemistry.
How do I manage Electric Blue Johannii's territorial behaviour?
Provide line-of-sight breaks using rocks, driftwood, and dense planting. A larger tank gives Electric Blue Johannii 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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