Can Delicate Blue-Eye and Mono Sebae (Brackish) Live Together?

Reviewed by Guidarium Editorial DeskUpdated May 4, 2026
Possible with Caution

Keeping Delicate Blue-Eye and Mono Sebae (Brackish) together is possible but requires caution due to potential behavioral clashes. Provide a spacious tank of at least 400 litres with plenty of hiding spots to reduce stress. Monitor behaviour closely, especially during the first few weeks.


At a Glance

Delicate Blue-Eye

Pseudomugil tenellus

Mono Sebae (Brackish)

Monodactylus sebae

🐠Family Group
Delicate Blue-Eye
Rainbowfish
Mono Sebae (Brackish)
Oddballs
Temperament
Delicate Blue-Eye
Peaceful (1/10)
Mono Sebae (Brackish)
Mostly Peaceful (4/10)
Temperature
✓ Compatible
Delicate Blue-Eye
25–32°C
Mono Sebae (Brackish)
24–28°C
pH Range
✓ Compatible
Delicate Blue-Eye
5–7.5
Mono Sebae (Brackish)
7.5–8.5
Hardness (dGH)
✓ Compatible
Delicate Blue-Eye
5–15
Mono Sebae (Brackish)
12–30
Water Type
✓ Compatible
Delicate Blue-Eye
Brackish Tolerant
Mono Sebae (Brackish)
Brackish Required
Flow Preference
✓ Compatible
Delicate Blue-Eye
Moderate
Mono Sebae (Brackish)
Moderate
Min Tank Volume
Combined: 400 L
Delicate Blue-Eye
60 L
Mono Sebae (Brackish)
400 L
Swimming Level
Shared: 1 zone
Delicate Blue-Eye
TopMiddle
Mono Sebae (Brackish)
Middle
🏷️Behavior Tags
Delicate Blue-Eye
Nano / Bite-sized (Predation Risk)Hyperactive / Fast SwimmerJumper (Lid Required)Fry Predator
Mono Sebae (Brackish)
Hyperactive / Fast SwimmerPlant DestroyerShrimp EaterAggressive Eater (Starves shy fish)
Stocking calculator

Can your tank handle Delicate Blue-Eye and Mono Sebae (Brackish)?

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.

Delicate Blue-Eye
Mono Sebae (Brackish)
Test both in my tank

Behaviour & Temperament

Delicate Blue-Eye is a peaceful species (1/10), while Mono Sebae (Brackish) is generally mild-mannered (4/10). This modest difference means Mono Sebae (Brackish) may occasionally assert dominance over Delicate Blue-Eye.

Delicate Blue-Eye and Mono Sebae (Brackish) 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: Shrimp eaters may also prey on very small nano fish.

Worth noting: Delicate Blue-Eye is a known jumper, so a tight-fitting lid is essential.

Water Parameters

The safe temperature window for both species falls between 25°C and 28°C. Aim for the midpoint of this range (around 26.5°C) for optimal comfort.

Both fish can tolerate a pH between 7.5 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 12–15 dGH. Regular testing will ensure conditions stay within this range.

Tank Setup

To house Delicate Blue-Eye and Mono Sebae (Brackish) together, plan for an aquarium of at least 400 litres with a minimum length of 150 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, Sand (Sifters), Smooth Gravel (Sensitive Barbels). Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Mono Sebae (Brackish) is a plant destroyer, which conflicts with Delicate Blue-Eye'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.

Why This Pairing Needs Extra Planning in Practice

This pairing usually fails when the tank is treated like a standard mixed community and the caution flags are ignored. Delicate Blue-Eye and Mono Sebae (Brackish) need extra room, more cover, and closer observation during the first few weeks so small aggression, feeding, or territory issues do not snowball into a long-term problem.

Suitable Tank Sizes

Standard aquarium sizes large enough for both Delicate Blue-Eye and Mono Sebae (Brackish).

Diet & Feeding

Feeding time deserves special attention with this pairing. Mono Sebae (Brackish) is a known shrimp eater and may prey on small invertebrates or nano fish like Delicate Blue-Eye.

Because Mono Sebae (Brackish) is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Delicate Blue-Eye receives an adequate share.

Frequently Asked Questions

Can Delicate Blue-Eye and Mono Sebae (Brackish) live together?

They can coexist, but the pairing requires careful monitoring. Provide ample space (at least 400 litres), plenty of hiding spots, and watch for signs of stress or aggression.

What size tank do Delicate Blue-Eye and Mono Sebae (Brackish) need?

A minimum of 400 litres (tank length at least 150 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 Delicate Blue-Eye and Mono Sebae (Brackish) together?

Keep the aquarium between 25°C and 28°C. A target of around 26.5°C sits comfortably within both species' preferred ranges.

Are Delicate Blue-Eye or Mono Sebae (Brackish) aggressive?

Delicate Blue-Eye is peaceful (1/10) and Mono Sebae (Brackish) is generally mild-mannered (4/10). Their similar temperaments generally lead to a peaceful coexistence.

What pH do Delicate Blue-Eye and Mono Sebae (Brackish) need?

Both species overlap in the 7.5–7.5 pH range. Consistency is key — avoid sudden swings, and test regularly to stay within this window.

Editorial Review

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
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