Can Boeseman's Rainbowfish and Least Killifish (Heterandria) Live Together?

Boeseman's Rainbowfish is a peaceful species (2/10), while Least Killifish (Heterandria) is peaceful (1/10). This modest difference means Boeseman's Rainbowfish may occasionally assert dominance over Least Killifish (Heterandria).

Boeseman's Rainbowfish and Least Killifish (Heterandria) both frequent the Top (Surface) and Middle (Open Water) 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: Boeseman's Rainbowfish is a known jumper, so a tight-fitting lid is essential.

To improve the chances of a peaceful coexistence in this community tank: A larger aquarium with ample hiding spots can help diffuse aggression and give the less dominant fish space to retreat.

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.

Both fish can tolerate a pH between 7 and 8. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 9–19 dGH. Regular testing will ensure conditions stay within this range.

To house Boeseman's Rainbowfish and Least Killifish (Heterandria) together, plan for an aquarium of at least 240 litres with a minimum length of 120 cm. This accounts for the larger species' space requirements with an additional 20 % buffer to reduce territorial tension.

Because this pairing requires extra vigilance, include plenty of hiding spots — caves, driftwood, and dense plant clusters — so the less dominant fish can retreat when needed.

Specific environmental needs for this combination include: Plants - lighly covered, Plants - Densely covered, Plants - Floating. Meeting these requirements will help both species thrive.

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

Feeding time deserves special attention with this pairing. Boeseman's Rainbowfish is an aggressive eater that may prevent Least Killifish (Heterandria) from getting enough food.

Because Boeseman's Rainbowfish is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Least Killifish (Heterandria) receives an adequate share.