Can Demasoni Cichlid (Mbuna) and Least Killifish (Heterandria) Live Together?

Demasoni Cichlid (Mbuna) is a highly aggressive species (9/10), while Least Killifish (Heterandria) is peaceful (1/10). This notable difference means Demasoni Cichlid (Mbuna) may occasionally assert dominance over Least Killifish (Heterandria).

Large aggression gap (8 points) between Demasoni Cichlid (Mbuna) and Least Killifish (Heterandria) increases stress risk for the more peaceful fish.

Demasoni Cichlid (Mbuna) and Least Killifish (Heterandria) both frequent the Bottom (Substrate) 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: Aggressive fish may bully and stress shy, slow-moving species. Hyperactive swimmers can stress shy, slow-moving species through constant motion.

To improve the chances of a peaceful coexistence in this community tank: Provide a significantly larger tank (at least 50% more volume than the minimum) to allow both Demasoni Cichlid (Mbuna) and Least Killifish (Heterandria) to establish separate territories. Add plenty of line-of-sight breaks using driftwood, rocks, and dense planting to reduce territorial confrontations. 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 24°C and 27°C. Aim for the midpoint of this range (around 25.5°C) for optimal comfort.

Both fish can tolerate a pH between 7.6 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 10–20 dGH. Regular testing will ensure conditions stay within this range. An aquarium test kit is recommended for monitoring.

To house Demasoni Cichlid (Mbuna) 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: Sand (Sifters), Established Algae (Otocinclus), Plants - Densely covered, Plants - Floating. Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Demasoni Cichlid (Mbuna) is a plant destroyer, which conflicts with Least Killifish (Heterandria)'s requirement for live plants. Compromise where possible or prioritise the more critical need.

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