Can Ruby Green Hap and Twig Catfish (Farlowella) Live Together?

Ruby Green Hap is a semi-aggressive species (7/10), while Twig Catfish (Farlowella) is peaceful (1/10). This notable difference means Ruby Green Hap may occasionally assert dominance over Twig Catfish (Farlowella).

Large aggression gap (6 points) between Ruby Green Hap and Twig Catfish (Farlowella) increases stress risk for the more peaceful fish.

Ruby Green Hap and Twig Catfish (Farlowella) 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: Hyperactive swimmers can stress shy, slow-moving species through constant motion.

The safe temperature window for both species falls between 24°C and 26°C. Aim for the midpoint of this range (around 25.0°C) for optimal comfort.

The pH requirements of Ruby Green Hap (7.5–8.6) and Twig Catfish (Farlowella) (6–7.2) do not overlap, making it impossible to satisfy both species simultaneously.

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

To house Ruby Green Hap and Twig Catfish (Farlowella) together, plan for an aquarium of at least 209 litres with a minimum length of 90 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), Established Algae (Otocinclus), Driftwood (Digestion/Hiding). Meeting these requirements will help both species thrive.

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

Ruby Green Hap and Twig Catfish (Farlowella) 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.