Can Flowerhorn Cichlid and Rachov's Killifish (Annual) Live Together?

Flowerhorn Cichlid is a highly aggressive species (10/10), while Rachov's Killifish (Annual) is generally mild-mannered (3/10). This notable difference means Flowerhorn Cichlid may occasionally assert dominance over Rachov's Killifish (Annual).

Large aggression gap (7 points) between Flowerhorn Cichlid and Rachov's Killifish (Annual) increases stress risk for the more peaceful fish.

Flowerhorn Cichlid and Rachov's Killifish (Annual) 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.

There is a critical concern: the Piscivore (Eats small/nano fish) behaviour of one fish directly conflicts with the Nano / Bite-sized (Predation Risk) trait of the other — piscivorous fish will prey on nano-sized tank mates..

Worth noting: Rachov's Killifish (Annual) is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 26°C and 26°C. Aim for the midpoint of this range (around 26.0°C) for optimal comfort.

Both fish can tolerate a pH between 7.4 and 7.5. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 9–12 dGH. Regular testing will ensure conditions stay within this range.

To house Flowerhorn Cichlid and Rachov's Killifish (Annual) together, plan for an aquarium of at least 280 litres with a minimum length of 120 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: Sand (Sifters), Smooth Gravel (Sensitive Barbels), Soil / Nutrient Rich, Leaf Litter/Blackwater, Plants - Densely covered. Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Flowerhorn Cichlid requires Sand (Sifters), while Rachov's Killifish (Annual) requires Soil / Nutrient Rich. These substrate types may be difficult to provide simultaneously. Flowerhorn Cichlid requires Smooth Gravel (Sensitive Barbels), while Rachov's Killifish (Annual) requires Soil / Nutrient Rich. These substrate types may be difficult to provide simultaneously. Flowerhorn Cichlid is a plant destroyer, which conflicts with Rachov's Killifish (Annual)'s requirement for live plants. Compromise where possible or prioritise the more critical need.

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

Flowerhorn Cichlid and Rachov's Killifish (Annual) 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.