Can Clown Killifish and Freshwater Harlequin Shrimp (Sulawesi) Live Together?

Clown Killifish is a peaceful species (2/10), while Freshwater Harlequin Shrimp (Sulawesi) is peaceful (0/10). This modest difference means Clown Killifish may occasionally assert dominance over Freshwater Harlequin Shrimp (Sulawesi).

In terms of spatial distribution, Clown Killifish prefers the Top (Surface) zone, whereas Freshwater Harlequin Shrimp (Sulawesi) 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.

Worth noting: Freshwater Harlequin Shrimp (Sulawesi) is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, Clown Killifish is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 26°C and 27°C. Aim for the midpoint of this range (around 26.5°C) for optimal comfort.

The pH requirements of Clown Killifish (5–7) and Freshwater Harlequin Shrimp (Sulawesi) (7.5–8.5) do not overlap, making it impossible to satisfy both species simultaneously.

For general hardness, the shared comfort zone is 4–8 dGH. Regular testing will ensure conditions stay within this range.

To house Clown Killifish and Freshwater Harlequin Shrimp (Sulawesi) together, plan for an aquarium of at least 38 litres with a minimum length of 45 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, Established Algae (Otocinclus), Smooth Gravel (Sensitive Barbels). 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.

Clown Killifish and Freshwater Harlequin Shrimp (Sulawesi) 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.