Can Beckford's Pencilfish and Congo Puffer (Potato Puffer) Live Together?

Beckford's Pencilfish is a peaceful species (2/10), while Congo Puffer (Potato Puffer) is highly aggressive (10/10). This notable difference means Congo Puffer (Potato Puffer) may occasionally assert dominance over Beckford's Pencilfish.

Large aggression gap (8 points) between Beckford's Pencilfish and Congo Puffer (Potato Puffer) increases stress risk for the more peaceful fish.

In terms of spatial distribution, Beckford's Pencilfish 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.

There is a critical concern: the Nano / Bite-sized (Predation Risk) behaviour of one fish directly conflicts with the Piscivore (Eats small/nano fish) trait of the other — piscivorous fish will prey on nano-sized tank mates..

Additional behavioural considerations to keep in mind: Aggressive fish may bully and stress shy, slow-moving species. Shrimp eaters may also prey on very small nano fish.

Worth noting: Beckford's Pencilfish is a known jumper, so a tight-fitting lid is essential.

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 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 Beckford's Pencilfish 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.

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: Plants - Densely covered, Plants - Floating, Leaf Litter/Blackwater, 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.

Beckford's Pencilfish and Congo Puffer (Potato Puffer) 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.

Feeding time deserves special attention with this pairing. Congo Puffer (Potato Puffer) is a known shrimp eater and may prey on small invertebrates or nano fish like Beckford's Pencilfish.