Can Clown Killifish and Masked Julie (Julidochromis) Live Together?
Clown Killifish and Masked Julie (Julidochromis) are not recommended as tank mates due to conflicting pH requirements and incompatible hardness ranges. Housing these species together is likely to result in stress, health problems, or direct harm to one or both fish.
At a Glance
Behaviour & Temperament
Clown Killifish is a peaceful species (2/10), while Masked Julie (Julidochromis) is moderately assertive (6/10). This notable difference means Masked Julie (Julidochromis) may occasionally assert dominance over Clown Killifish.
In terms of spatial distribution, Clown Killifish prefers the Top (Surface) zone, whereas Masked Julie (Julidochromis) occupies the Bottom (Substrate) 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.
Worth noting: Clown Killifish 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 27°C. Aim for the midpoint of this range (around 25.0°C) for optimal comfort.
The pH requirements of Clown Killifish (5–7) and Masked Julie (Julidochromis) (8–9) do not overlap, making it impossible to satisfy both species simultaneously.
Hardness requirements are incompatible: Clown Killifish needs 1–8 dGH while Masked Julie (Julidochromis) requires 10–20 dGH. An aquarium test kit is recommended for monitoring.
Tank Setup
To house Clown Killifish and Masked Julie (Julidochromis) together, plan for an aquarium of at least 72 litres with a minimum length of 60 cm. This accounts for the larger species' space requirements with an additional 20 % buffer to reduce territorial tension.
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: Plants - Floating, Plants - Densely covered, Leaf Litter/Blackwater, Sand (Sifters). 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.
Find the right tank equipment
Browse tanks, décor, and equipment suited for this setup.
Frequently Asked Questions
Can Clown Killifish and Masked Julie (Julidochromis) live together?▾
No. This combination is not recommended. Key incompatibilities — such as critical behavioural conflicts — make cohabitation unsafe.
What size tank do Clown Killifish and Masked Julie (Julidochromis) need?▾
A minimum of 72 litres (tank length at least 60 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 Clown Killifish and Masked Julie (Julidochromis) together?▾
Keep the aquarium between 23°C and 27°C. A target of around 25.0°C sits comfortably within both species' preferred ranges.
Are Clown Killifish or Masked Julie (Julidochromis) aggressive?▾
Clown Killifish is peaceful (2/10) and Masked Julie (Julidochromis) is moderately assertive (6/10). The gap in aggression levels means the calmer fish may experience stress from the more assertive one.
What pH do Clown Killifish and Masked Julie (Julidochromis) need?▾
Their pH requirements do not overlap. Clown Killifish prefers 5–7, while Masked Julie (Julidochromis) needs 8–9. This makes them incompatible in the same water chemistry.
How do I manage Masked Julie (Julidochromis)'s territorial behaviour?▾
Provide line-of-sight breaks using rocks, driftwood, and dense planting. A larger tank gives Masked Julie (Julidochromis) 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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