Can Least Killifish (Heterandria) and Rio Negro Dwarf Cichlid Live Together?

Least Killifish (Heterandria) is a peaceful species (1/10), while Rio Negro Dwarf Cichlid is semi-aggressive (7/10). This notable difference means Rio Negro Dwarf Cichlid may occasionally assert dominance over Least Killifish (Heterandria).

Large aggression gap (6 points) between Least Killifish (Heterandria) and Rio Negro Dwarf Cichlid increases stress risk for the more peaceful fish.

Least Killifish (Heterandria) and Rio Negro Dwarf Cichlid both frequent the 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: Aggressive fish may bully and stress shy, slow-moving species. Shrimp eaters may also prey on very small nano fish.

The safe temperature window for both species falls between 22°C and 27°C. Aim for the midpoint of this range (around 24.5°C) for optimal comfort.

The pH requirements of Least Killifish (Heterandria) (7–8) and Rio Negro Dwarf Cichlid (4–6.5) do not overlap, making it impossible to satisfy both species simultaneously.

For general hardness, the shared comfort zone is 5–5 dGH. Regular testing will ensure conditions stay within this range.

To house Least Killifish (Heterandria) and Rio Negro Dwarf Cichlid together, plan for an aquarium of at least 110 litres with a minimum length of 80 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: Plants - Densely covered, Plants - Floating, Leaf Litter/Blackwater, Driftwood (Digestion/Hiding), Sand (Sifters). 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.

Least Killifish (Heterandria) and Rio Negro Dwarf Cichlid 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. Rio Negro Dwarf Cichlid is a known shrimp eater and may prey on small invertebrates or nano fish like Least Killifish (Heterandria).