Can Blue Back Blue Eye and Red Tailed Black Shark Live Together?
Blue Back Blue Eye and Red Tailed Black Shark are not recommended as tank mates due to incompatible water types. 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 Blue Back Blue Eye and Red Tailed Black Shark?
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
Blue Back Blue Eye is a peaceful species (2/10), while Red Tailed Black Shark is semi-aggressive (7/10). This notable difference means Red Tailed Black Shark may occasionally assert dominance over Blue Back Blue Eye.
Blue Back Blue Eye and Red Tailed Black Shark 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.
Worth noting: Blue Back Blue Eye is a known jumper, so a tight-fitting lid is essential.
Water Parameters
The safe temperature window for both species falls between 22°C and 28°C. Aim for the midpoint of this range (around 25.0°C) for optimal comfort.
Both fish can tolerate a pH between 7 and 7.5. Maintaining a stable value within this band is more important than hitting an exact number.
For general hardness, the shared comfort zone is 10–15 dGH. Regular testing will ensure conditions stay within this range.
Crucially, these species require different water types — one needs freshwater while the other requires brackish conditions. This is a hard barrier to keeping them together.
Tank Setup
To house Blue Back Blue Eye and Red Tailed Black Shark together, plan for an aquarium of at least 208 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: Driftwood (Digestion/Hiding), Sand (Sifters), Plants - Densely covered, Smooth Gravel (Sensitive Barbels). 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
Blue Back Blue Eye and Red Tailed Black Shark 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 Blue Back Blue Eye and Red Tailed Black Shark.
55 Gallon Standard
60 Gallon Breeder
75 Gallon Standard
90 Gallon Standard
125 Gallon Standard
150 Gallon High
Frequently Asked Questions
Can Blue Back Blue Eye and Red Tailed Black Shark live together?
No. This combination is not recommended. Key incompatibilities — such as different water type needs — make cohabitation unsafe.
What size tank do Blue Back Blue Eye and Red Tailed Black Shark need?
A minimum of 208 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 Blue Back Blue Eye and Red Tailed Black Shark together?
Keep the aquarium between 22°C and 28°C. A target of around 25.0°C sits comfortably within both species' preferred ranges.
Are Blue Back Blue Eye or Red Tailed Black Shark aggressive?
Blue Back Blue Eye is peaceful (2/10) and Red Tailed Black Shark is semi-aggressive (7/10). The gap in aggression levels means the calmer fish may experience stress from the more assertive one.
What pH do Blue Back Blue Eye and Red Tailed Black Shark need?
Both species overlap in the 7–7.5 pH range. Consistency is key — avoid sudden swings, and test regularly to stay within this window.
How do I manage Red Tailed Black Shark's territorial behaviour?
Provide line-of-sight breaks using rocks, driftwood, and dense planting. A larger tank gives Red Tailed Black Shark 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 2, 2026
- Last updated
- May 2, 2026
- Issues or corrections?
- Contact the editorial team
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