Can Freshwater Flounder and Lesser Spiny Eel Live Together?

Freshwater Flounder is a peaceful species (2/10), while Lesser Spiny Eel is generally mild-mannered (4/10). This modest difference means Lesser Spiny Eel may occasionally assert dominance over Freshwater Flounder.

Freshwater Flounder and Lesser Spiny Eel both frequent the Bottom (Substrate) 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: Freshwater Flounder is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, Lesser Spiny Eel is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 23°C and 26°C. Aim for the midpoint of this range (around 24.5°C) for optimal comfort.

Both fish can tolerate a pH between 7.5 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 10–15 dGH. Regular testing will ensure conditions stay within this range.

To house Freshwater Flounder and Lesser Spiny Eel 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.

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: Sand (Sifters), Smooth Gravel (Sensitive Barbels), 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.