Can Betta Macrostoma and Freshwater Harlequin Shrimp (Sulawesi) Live Together?

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

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

Betta Macrostoma and Freshwater Harlequin Shrimp (Sulawesi) both frequent the Bottom (Substrate) region of the setup. This overlap can increase competition for space, so providing ample room and cover is important to keep both species comfortable.

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: Shrimp eaters may also prey on very small nano fish.

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

There is no temperature overlap between Betta Macrostoma (20–25°C) and Freshwater Harlequin Shrimp (Sulawesi) (26–30°C). This fundamental mismatch makes long-term cohabitation impractical.

The pH requirements of Betta Macrostoma (4–6) 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 4–5 dGH. Regular testing will ensure conditions stay within this range.

To house Betta Macrostoma and Freshwater Harlequin Shrimp (Sulawesi) together, plan for an aquarium of at least 80 litres with a minimum length of 60 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: Leaf Litter/Blackwater, Driftwood (Digestion/Hiding), Plants - Floating, 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.

Betta Macrostoma 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.

Feeding time deserves special attention with this pairing. Betta Macrostoma is a known shrimp eater and may prey on small invertebrates or nano fish like Freshwater Harlequin Shrimp (Sulawesi).