Can Brown Hoplo Catfish and Cairns Rainbowfish Live Together?

Both Brown Hoplo Catfish and Cairns Rainbowfish are peaceful species with an aggression score of 2/10. Their matching temperaments mean neither fish is likely to dominate the other in a shared aquarium.

Brown Hoplo Catfish and Cairns Rainbowfish 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.

Worth noting: Brown Hoplo Catfish is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 20°C and 26°C. Aim for the midpoint of this range (around 23.0°C) for optimal comfort.

Both fish can tolerate a pH between 6.5 and 7.6. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 4–10 dGH. Regular testing will ensure conditions stay within this range.

To house Brown Hoplo Catfish and Cairns Rainbowfish together, plan for an aquarium of at least 200 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.

Because this pairing requires extra vigilance, include plenty of hiding spots — caves, driftwood, and dense plant clusters — so the less dominant fish can retreat when needed.

Specific environmental needs for this combination include: Sand (Sifters), Smooth Gravel (Sensitive Barbels), Driftwood (Digestion/Hiding), Leaf Litter/Blackwater. Meeting these requirements will help both species thrive.

Brown Hoplo Catfish prefers Low (Still Water) flow while Cairns Rainbowfish needs High (River/Stream) flow. Consider positioning filter outlets and using baffles to create zones of different current intensity within the same tank.

This pairing usually fails when the tank is treated like a standard mixed community and the caution flags are ignored. Brown Hoplo Catfish and Cairns Rainbowfish need extra room, more cover, and closer observation during the first few weeks so small aggression, feeding, or territory issues do not snowball into a long-term problem.