Can Arrowhead Puffer and MacCulloch's Rainbowfish (Dwarf Rainbowfish) Live Together?

Arrowhead Puffer is a highly aggressive species (10/10), while MacCulloch's Rainbowfish (Dwarf Rainbowfish) is peaceful (2/10). This notable difference means Arrowhead Puffer may occasionally assert dominance over MacCulloch's Rainbowfish (Dwarf Rainbowfish).

Large aggression gap (8 points) between Arrowhead Puffer and MacCulloch's Rainbowfish (Dwarf Rainbowfish) increases stress risk for the more peaceful fish.

In terms of spatial distribution, Arrowhead Puffer prefers the Bottom (Substrate) zone, whereas MacCulloch's Rainbowfish (Dwarf Rainbowfish) occupies the Top (Surface) and Middle (Open Water) zones. Because they use different levels of the water column, territorial disputes are less likely and the tank will appear more balanced.

Additional behavioural considerations to keep in mind: Hyperactive swimmers can stress shy, slow-moving species through constant motion.

Worth noting: MacCulloch's Rainbowfish (Dwarf Rainbowfish) is a known jumper, so a tight-fitting lid is essential.

To improve the chances of a peaceful coexistence in this community tank: 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 22°C and 28°C. Aim for the midpoint of this range (around 25.0°C) for optimal comfort.

Both fish can tolerate a pH between 6.5 and 7.5. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 5–15 dGH. Regular testing will ensure conditions stay within this range.

To house Arrowhead Puffer and MacCulloch's Rainbowfish (Dwarf Rainbowfish) together, plan for an aquarium of at least 114 litres with a minimum length of 80 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), Plants - Densely covered. 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.

This pairing usually fails when the tank is treated like a standard mixed community and the caution flags are ignored. Arrowhead Puffer and MacCulloch's Rainbowfish (Dwarf 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.