Can Black Ghost Knifefish and Licorice Gourami Live Together?

Black Ghost Knifefish is a moderately assertive species (6/10), while Licorice Gourami is peaceful (2/10). This notable difference means Black Ghost Knifefish may occasionally assert dominance over Licorice Gourami.

Black Ghost Knifefish and Licorice Gourami both frequent the Bottom (Substrate) and Middle (Open Water) region of the setup. This overlap can increase competition for space, so providing ample room and cover is important to keep both species comfortable.

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

Additional behavioural considerations to keep in mind: Shrimp eaters may also prey on very small nano fish.

Worth noting: Black Ghost Knifefish is nocturnal and will be most active after lights-out, naturally reducing daytime encounters.

The safe temperature window for both species falls between 23°C and 28°C. Aim for the midpoint of this range (around 25.5°C) for optimal comfort.

Both fish can tolerate a pH between 6 and 6. Maintaining a stable value within this band is more important than hitting an exact number.

Hardness requirements are incompatible: Black Ghost Knifefish needs 5–15 dGH while Licorice Gourami requires 0–4 dGH.

To house Black Ghost Knifefish and Licorice Gourami together, plan for an aquarium of at least 450 litres with a minimum length of 150 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: Smooth Gravel (Sensitive Barbels), Driftwood (Digestion/Hiding), Sand (Sifters), Leaf Litter/Blackwater, Plants - Densely covered, Plants - Floating. 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.

Black Ghost Knifefish and Licorice Gourami 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. Black Ghost Knifefish is a known shrimp eater and may prey on small invertebrates or nano fish like Licorice Gourami.