Can Betta Macrostoma and Koi Live Together?

Betta Macrostoma is a moderately assertive species (6/10), while Koi is peaceful (2/10). This notable difference means Betta Macrostoma may occasionally assert dominance over Koi.

Betta Macrostoma and Koi both frequent the Top (Surface), Middle (Open Water), and 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.

Additional behavioural considerations to keep in mind: Hyperactive swimmers can stress shy, slow-moving species through constant motion. Aggressive eaters may outcompete shy fish for food, leading to malnutrition.

Worth noting: Betta Macrostoma is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 20°C and 25°C. Aim for the midpoint of this range (around 22.5°C) for optimal comfort.

The pH requirements of Betta Macrostoma (4–6) and Koi (6.5–8.5) 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 Koi together, plan for an aquarium of at least 3785 litres with a minimum length of 300 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, Sand (Sifters), 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 Koi 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. Koi is an aggressive eater that may prevent Betta Macrostoma from getting enough food.

Because Koi is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Betta Macrostoma receives an adequate share.