Can Clown Killifish and Electric Blue Johannii Live Together?

Clown Killifish is a peaceful species (2/10), while Electric Blue Johannii is semi-aggressive (8/10). This notable difference means Electric Blue Johannii may occasionally assert dominance over Clown Killifish.

Large aggression gap (6 points) between Clown Killifish and Electric Blue Johannii increases stress risk for the more peaceful fish.

In terms of spatial distribution, Clown Killifish prefers the Top (Surface) zone, whereas Electric Blue Johannii occupies the Middle (Open Water) and Bottom (Substrate) zones. 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: Aggressive fish may bully and stress shy, slow-moving species. Hyperactive swimmers can stress shy, slow-moving species through constant motion.

Worth noting: Clown Killifish is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 24°C and 27°C. Aim for the midpoint of this range (around 25.5°C) for optimal comfort.

The pH requirements of Clown Killifish (5–7) and Electric Blue Johannii (7.8–8.6) do not overlap, making it impossible to satisfy both species simultaneously.

Hardness requirements are incompatible: Clown Killifish needs 1–8 dGH while Electric Blue Johannii requires 10–25 dGH.

To house Clown Killifish and Electric Blue Johannii together, plan for an aquarium of at least 184 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: Plants - Floating, Plants - Densely covered, Leaf Litter/Blackwater, Sand (Sifters), Established Algae (Otocinclus). Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Electric Blue Johannii is a plant destroyer, which conflicts with Clown Killifish's requirement for live plants. Compromise where possible or prioritise the more critical need.

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

Clown Killifish and Electric Blue Johannii 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.