Can Flag Tetra and Trewavas' Cichlid Live Together?

Flag Tetra is a peaceful species (1/10), while Trewavas' Cichlid is semi-aggressive (8/10). This notable difference means Trewavas' Cichlid may occasionally assert dominance over Flag Tetra.

Large aggression gap (7 points) between Flag Tetra and Trewavas' Cichlid increases stress risk for the more peaceful fish.

Flag Tetra and Trewavas' 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.

The safe temperature window for both species falls between 24°C and 28°C. Aim for the midpoint of this range (around 26.0°C) for optimal comfort.

The pH requirements of Flag Tetra (5.5–7.5) and Trewavas' Cichlid (7.8–8.6) do not overlap, making it impossible to satisfy both species simultaneously.

For general hardness, the shared comfort zone is 10–12 dGH. Regular testing will ensure conditions stay within this range.

To house Flag Tetra and Trewavas' Cichlid together, plan for an aquarium of at least 252 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: Plants - Densely covered, Leaf Litter/Blackwater, Sand (Sifters), Established Algae (Otocinclus). Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Trewavas' Cichlid is a plant destroyer, which conflicts with Flag Tetra'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.

Flag Tetra and Trewavas' 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.