Can Balloon Molly and Congo Puffer (Potato Puffer) Live Together?

Balloon Molly is a generally mild-mannered species (3/10), while Congo Puffer (Potato Puffer) is highly aggressive (10/10). This notable difference means Congo Puffer (Potato Puffer) may occasionally assert dominance over Balloon Molly.

Large aggression gap (7 points) between Balloon Molly and Congo Puffer (Potato Puffer) increases stress risk for the more peaceful fish.

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

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 Balloon Molly and Congo Puffer (Potato Puffer) 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 24°C and 28°C. Aim for the midpoint of this range (around 26.0°C) for optimal comfort.

Both fish can tolerate a pH between 7 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 12–15 dGH. Regular testing will ensure conditions stay within this range.

To house Balloon Molly and Congo Puffer (Potato Puffer) together, plan for an aquarium of at least 110 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: Established Algae (Otocinclus), Plants - Densely covered, Sand (Sifters). Meeting these requirements will help both species thrive.

Both species do well with low (still water) 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. Balloon Molly and Congo Puffer (Potato Puffer) 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.