Can Australian Smelt and Black Bullhead Catfish Live Together?

Australian Smelt is a peaceful species (1/10), while Black Bullhead Catfish is semi-aggressive (7/10). This notable difference means Black Bullhead Catfish may occasionally assert dominance over Australian Smelt.

Large aggression gap (6 points) between Australian Smelt and Black Bullhead Catfish increases stress risk for the more peaceful fish.

In terms of spatial distribution, Australian Smelt prefers the Top (Surface) and Middle (Open Water) zones, whereas Black Bullhead Catfish 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.

Additional behavioural considerations to keep in mind: Aggressive fish may bully and stress shy, slow-moving species. Aggressive eaters may outcompete shy fish for food, leading to malnutrition.

Worth noting: Black Bullhead Catfish is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, Australian Smelt is a known jumper, so a tight-fitting lid is essential.

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 Australian Smelt and Black Bullhead Catfish 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 15°C and 24°C. Aim for the midpoint of this range (around 19.5°C) for optimal comfort.

Both fish can tolerate a pH between 6.5 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 5–20 dGH. Regular testing will ensure conditions stay within this range.

To house Australian Smelt and Black Bullhead Catfish together, plan for an aquarium of at least 560 litres with a minimum length of 180 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: Plants - lighly covered, Smooth Gravel (Sensitive Barbels), Sand (Sifters), 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. Black Bullhead Catfish is an aggressive eater that may prevent Australian Smelt from getting enough food.

Because Black Bullhead Catfish is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Australian Smelt receives an adequate share.