Can Dusky Millions Fish and Red Terror (Festa's Cichlid) Live Together?

Dusky Millions Fish is a peaceful species (2/10), while Red Terror (Festa's Cichlid) is highly aggressive (10/10). This notable difference means Red Terror (Festa's Cichlid) may occasionally assert dominance over Dusky Millions Fish.

Large aggression gap (8 points) between Dusky Millions Fish and Red Terror (Festa's Cichlid) increases stress risk for the more peaceful fish.

Dusky Millions Fish and Red Terror (Festa's Cichlid) both frequent the 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.

There is no temperature overlap between Dusky Millions Fish (16–24°C) and Red Terror (Festa's Cichlid) (25–29°C). This fundamental mismatch makes long-term cohabitation impractical.

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 8–18 dGH. Regular testing will ensure conditions stay within this range.

To house Dusky Millions Fish and Red Terror (Festa's Cichlid) together, plan for an aquarium of at least 450 litres with a minimum length of 150 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, Established Algae (Otocinclus), Sand (Sifters), Driftwood (Digestion/Hiding), Smooth Gravel (Sensitive Barbels). Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Red Terror (Festa's Cichlid) is a plant destroyer, which conflicts with Dusky Millions Fish's requirement for live plants. Compromise where possible or prioritise the more critical need.

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

Dusky Millions Fish and Red Terror (Festa's 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.