Can Freshwater Harlequin Shrimp (Sulawesi) and Redtail Splitfin Live Together?

Freshwater Harlequin Shrimp (Sulawesi) is a peaceful species (0/10), while Redtail Splitfin is moderately assertive (6/10). This notable difference means Redtail Splitfin may occasionally assert dominance over Freshwater Harlequin Shrimp (Sulawesi).

Large aggression gap (6 points) between Freshwater Harlequin Shrimp (Sulawesi) and Redtail Splitfin increases stress risk for the more peaceful fish.

In terms of spatial distribution, Freshwater Harlequin Shrimp (Sulawesi) prefers the Bottom (Substrate) zone, whereas Redtail Splitfin 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.

Additional behavioural considerations to keep in mind: Hyperactive swimmers can stress shy, slow-moving species through constant motion.

Worth noting: Freshwater Harlequin Shrimp (Sulawesi) is nocturnal and will be most active after lights-out, naturally reducing daytime encounters.

The safe temperature window for both species falls between 26°C and 26°C. Aim for the midpoint of this range (around 26.0°C) for optimal comfort.

Both fish can tolerate a pH between 7.5 and 8.5. Maintaining a stable value within this band is more important than hitting an exact number.

Hardness requirements are incompatible: Freshwater Harlequin Shrimp (Sulawesi) needs 4–8 dGH while Redtail Splitfin requires 10–25 dGH.

To house Freshwater Harlequin Shrimp (Sulawesi) and Redtail Splitfin together, plan for an aquarium of at least 110 litres with a minimum length of 80 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: Established Algae (Otocinclus), Smooth Gravel (Sensitive Barbels), Plants - Densely covered. 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.

Freshwater Harlequin Shrimp (Sulawesi) and Redtail Splitfin 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.