Can Least Killifish (Heterandria) and Zebra Danio Live Together?

Least Killifish (Heterandria) is a peaceful species (1/10), while Zebra Danio is generally mild-mannered (3/10). This modest difference means Zebra Danio may occasionally assert dominance over Least Killifish (Heterandria).

Least Killifish (Heterandria) and Zebra Danio 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: Zebra Danio 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. Keep fin nippers in larger groups to distribute nipping behaviour among conspecifics rather than tank mates.

The safe temperature window for both species falls between 18°C and 26°C. Aim for the midpoint of this range (around 22.0°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 5–20 dGH. Regular testing will ensure conditions stay within this range. An aquarium test kit is recommended for monitoring.

To house Least Killifish (Heterandria) and Zebra Danio together, plan for an aquarium of at least 46 litres with a minimum length of 60 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 - Densely covered, Plants - Floating, Smooth Gravel (Sensitive Barbels). Meeting these requirements will help both species thrive.

Least Killifish (Heterandria) prefers Low (Still Water) flow while Zebra Danio needs High (River/Stream) flow. Consider positioning filter outlets and using baffles to create zones of different current intensity within the same tank.

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

Because Zebra Danio 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.