Can Boeseman's Rainbowfish and Jack Dempsey Live Together?

Boeseman's Rainbowfish is a peaceful species (2/10), while Jack Dempsey is semi-aggressive (8/10). This notable difference means Jack Dempsey may occasionally assert dominance over Boeseman's Rainbowfish.

Large aggression gap (6 points) between Boeseman's Rainbowfish and Jack Dempsey increases stress risk for the more peaceful fish.

Boeseman's Rainbowfish and Jack Dempsey 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: Boeseman's Rainbowfish is a known jumper, so a tight-fitting lid is essential.

To improve the chances of a peaceful coexistence in this community tank: Provide a significantly larger tank (at least 50% more volume than the minimum) to allow both Boeseman's Rainbowfish and Jack Dempsey to establish separate territories. Add plenty of line-of-sight breaks using driftwood, rocks, and dense planting to reduce territorial confrontations. A larger aquarium with ample hiding spots can help diffuse aggression and give the less dominant fish space to retreat.

The safe temperature window for both species falls between 26°C and 30°C. Aim for the midpoint of this range (around 28.0°C) for optimal comfort.

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 9–15 dGH. Regular testing will ensure conditions stay within this range.

To house Boeseman's Rainbowfish and Jack Dempsey together, plan for an aquarium of at least 240 litres with a minimum length of 120 cm. This accounts for the larger species' space requirements with an additional 20 % buffer to reduce territorial tension.

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: Plants - lighly covered, Sand (Sifters), Driftwood (Digestion/Hiding), Smooth Gravel (Sensitive Barbels). Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Jack Dempsey is a plant destroyer, which conflicts with Boeseman's Rainbowfish'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.