Can Fire Eel and Mono Sebae (Brackish) Live Together?

Both Fire Eel and Mono Sebae (Brackish) are generally mild-mannered species with an aggression score of 4/10. Their matching temperaments mean neither fish is likely to dominate the other in a shared aquarium.

In terms of spatial distribution, Fire Eel prefers the Bottom (Substrate) zone, whereas Mono Sebae (Brackish) occupies the Middle (Open Water) zone. 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. Aggressive eaters may outcompete shy fish for food, leading to malnutrition.

Worth noting: Fire Eel is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, Fire Eel 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 7.5 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 12–15 dGH. Regular testing will ensure conditions stay within this range.

Crucially, these species require different water types — one needs freshwater while the other requires brackish conditions. This is a hard barrier to keeping them together.

To house Fire Eel and Mono Sebae (Brackish) together, plan for an aquarium of at least 816 litres with a minimum length of 180 cm. This accounts for the larger species' space requirements with an additional 20 % buffer to reduce territorial tension.

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), Driftwood (Digestion/Hiding). 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.

Feeding time deserves special attention with this pairing. Mono Sebae (Brackish) is an aggressive eater that may prevent Fire Eel from getting enough food.

Because Mono Sebae (Brackish) is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Fire Eel receives an adequate share.