Can Freshwater Sole and Gertrude's Spotted Blue-eye Live Together?

Reviewed by Guidarium Editorial DeskUpdated May 6, 2026
Not Recommended

Freshwater Sole and Gertrude's Spotted Blue-eye are not recommended as tank mates due to piscivorous fish will prey on nano-sized tank mates.. Housing these species together is likely to result in stress, health problems, or direct harm to one or both fish.


At a Glance

Freshwater Sole

Brachirus selheimi

Gertrude's Spotted Blue-eye

Pseudomugil gertrudae

🐠Family Group
Freshwater Sole
Oddballs
Gertrude's Spotted Blue-eye
Rainbowfish
Temperament
Freshwater Sole
Mostly Peaceful (4/10)
Gertrude's Spotted Blue-eye
Peaceful (2/10)
Temperature
✓ Compatible
Freshwater Sole
22–28°C
Gertrude's Spotted Blue-eye
21–28°C
pH Range
✓ Compatible
Freshwater Sole
6.5–7.8
Gertrude's Spotted Blue-eye
6–7.5
Hardness (dGH)
✓ Compatible
Freshwater Sole
5–15
Gertrude's Spotted Blue-eye
5–15
Water Type
✓ Compatible
Freshwater Sole
Brackish Tolerant
Gertrude's Spotted Blue-eye
Freshwater Only
Flow Preference
✓ Compatible
Freshwater Sole
Low
Gertrude's Spotted Blue-eye
Moderate
Min Tank Volume
Combined: 110 L
Freshwater Sole
110 L
Gertrude's Spotted Blue-eye
38 L
Swimming Level
✓ Different zones
Freshwater Sole
Bottom
Gertrude's Spotted Blue-eye
TopMiddle
🏷️Behavior Tags
Freshwater Sole
Piscivore (Eats small/nano fish)Shrimp EaterFry PredatorDigger (Disturbs Substrate)Shy / Slow Moving (Easily Stressed)Nocturnal
Gertrude's Spotted Blue-eye
Nano / Bite-sized (Predation Risk)Hyperactive / Fast SwimmerJumper (Lid Required)Fry Predator
Stocking calculator

Can your tank handle Freshwater Sole and Gertrude's Spotted Blue-eye?

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.

Freshwater Sole
Gertrude's Spotted Blue-eye
Test both in my tank

Behaviour & Temperament

Freshwater Sole is a generally mild-mannered species (4/10), while Gertrude's Spotted Blue-eye is peaceful (2/10). This modest difference means Freshwater Sole may occasionally assert dominance over Gertrude's Spotted Blue-eye.

In terms of spatial distribution, Freshwater Sole prefers the Bottom (Substrate) zone, whereas Gertrude's Spotted Blue-eye occupies the Top (Surface) and Middle (Open Water) zones. Because they use different levels of the water column, territorial disputes are less likely and the tank will appear more balanced.

There is a critical concern: the Piscivore (Eats small/nano fish) behaviour of one fish directly conflicts with the Nano / Bite-sized (Predation Risk) trait of the other — piscivorous fish will prey on nano-sized tank mates..

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: Freshwater Sole is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, Gertrude's Spotted 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 6.5 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 5–15 dGH. Regular testing will ensure conditions stay within this range.

Tank Setup

To house Freshwater Sole and Gertrude's Spotted Blue-eye together, plan for an aquarium of at least 110 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), Plants - Densely covered, Plants - Floating, Leaf Litter/Blackwater. Meeting these requirements will help both species thrive.

Both species do well with low (still water) water movement, so a standard filtration setup rated for the tank volume should suffice.

Why This Pairing Usually Fails in Practice

Freshwater Sole and Gertrude's Spotted Blue-eye 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 Freshwater Sole and Gertrude's Spotted Blue-eye.

Show 10 more tank sizes

Diet & Feeding

Feeding time deserves special attention with this pairing. Freshwater Sole is a known shrimp eater and may prey on small invertebrates or nano fish like Gertrude's Spotted Blue-eye.

Frequently Asked Questions

Can Freshwater Sole and Gertrude's Spotted Blue-eye live together?

No. This combination is not recommended. Key incompatibilities — such as critical behavioural conflicts — make cohabitation unsafe.

What size tank do Freshwater Sole and Gertrude's Spotted Blue-eye need?

A minimum of 110 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 Freshwater Sole and Gertrude's Spotted Blue-eye 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 Freshwater Sole or Gertrude's Spotted Blue-eye aggressive?

Freshwater Sole is generally mild-mannered (4/10) and Gertrude's Spotted Blue-eye is peaceful (2/10). Their similar temperaments generally lead to a peaceful coexistence.

What pH do Freshwater Sole and Gertrude's Spotted Blue-eye need?

Both species overlap in the 6.5–7.5 pH range. Consistency is key — avoid sudden swings, and test regularly to stay within this window.

Does Freshwater Sole being nocturnal affect compatibility?

Freshwater Sole 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 Freshwater Sole during evening hours.

Editorial Review

Guidarium Editorial Desk

Reviewed against Guidarium care, stocking, and compatibility standards. Read the editorial policy.

Last reviewed
May 6, 2026
Last updated
May 6, 2026
Issues or corrections?
Contact the editorial team

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