Can Blue Back Blue Eye and Peacock Eel Live Together?

Reviewed by Guidarium Editorial DeskUpdated May 7, 2026
Not Recommended

Blue Back Blue Eye and Peacock Eel 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

Blue Back Blue Eye

Pseudomugil cyanodorsalis

Peacock Eel

Macrognathus siamensis

🐠Family Group
Blue Back Blue Eye
Rainbowfish
Peacock Eel
Oddballs
Temperament
Blue Back Blue Eye
Peaceful (2/10)
Peacock Eel
Peaceful (2/10)
Temperature
✓ Compatible
Blue Back Blue Eye
22–30°C
Peacock Eel
23–28°C
pH Range
✓ Compatible
Blue Back Blue Eye
7–8.5
Peacock Eel
6.5–8
Hardness (dGH)
✓ Compatible
Blue Back Blue Eye
10–30
Peacock Eel
5–15
Water Type
✗ No overlap
Blue Back Blue Eye
Brackish Required
Peacock Eel
Freshwater Only
Flow Preference
✓ Compatible
Blue Back Blue Eye
Moderate
Peacock Eel
Low
Min Tank Volume
Combined: 150 L
Blue Back Blue Eye
38 L
Peacock Eel
150 L
Swimming Level
✓ Different zones
Blue Back Blue Eye
TopMiddle
Peacock Eel
Bottom
🏷️Behavior Tags
Blue Back Blue Eye
Nano / Bite-sized (Predation Risk)Jumper (Lid Required)Hyperactive / Fast SwimmerFry Predator
Peacock Eel
Digger (Disturbs Substrate)Jumper (Lid Required)NocturnalShy / Slow Moving (Easily Stressed)Shrimp EaterFry PredatorAggressive Eater (Starves shy fish)
Stocking calculator

Can your tank handle Blue Back Blue Eye and Peacock Eel?

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.

Blue Back Blue Eye
Peacock Eel
Test both in my tank

Behaviour & Temperament

Both Blue Back Blue Eye and Peacock Eel 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.

In terms of spatial distribution, Blue Back Blue Eye prefers the Top (Surface) and Middle (Open Water) zones, whereas Peacock Eel occupies the Bottom (Substrate) zone. Because they use different levels of the water column, territorial disputes are less likely and the tank will appear more balanced.

Additional behavioural considerations to keep in mind: Hyperactive swimmers can stress shy, slow-moving species through constant motion. Shrimp eaters may also prey on very small nano fish.

Worth noting: Peacock Eel is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, 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 23°C and 28°C. Aim for the midpoint of this range (around 25.5°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 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 Peacock Eel 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.

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), Smooth Gravel (Sensitive Barbels), Plants - Densely covered. 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 Peacock Eel 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 Peacock Eel.

Show 9 more tank sizes

Diet & Feeding

Feeding time deserves special attention with this pairing. Peacock Eel is a known shrimp eater and may prey on small invertebrates or nano fish like Blue Back Blue Eye.

Because Peacock Eel is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Blue Back Blue Eye receives an adequate share.

Frequently Asked Questions

Can Blue Back Blue Eye and Peacock Eel 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 Peacock Eel 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 Blue Back Blue Eye and Peacock Eel together?

Keep the aquarium between 23°C and 28°C. A target of around 25.5°C sits comfortably within both species' preferred ranges.

Are Blue Back Blue Eye or Peacock Eel aggressive?

Blue Back Blue Eye is peaceful (2/10) and Peacock Eel is peaceful (2/10). Their similar temperaments generally lead to a peaceful coexistence.

What pH do Blue Back Blue Eye and Peacock Eel need?

Both species overlap in the 7–8 pH range. Consistency is key — avoid sudden swings, and test regularly to stay within this window.

Does Peacock Eel being nocturnal affect compatibility?

Peacock Eel is most active after lights-out, which naturally reduces daytime encounters with its tank mate. This can actually be beneficial, as both fish get undisturbed time to feed and explore. Just ensure food reaches Peacock Eel during evening hours.

Editorial Review

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?
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