Can Frogmouth Catfish and Threadfin Rainbowfish Live Together?

Frogmouth Catfish is a semi-aggressive species (7/10), while Threadfin Rainbowfish is peaceful (1/10). This notable difference means Frogmouth Catfish may occasionally assert dominance over Threadfin Rainbowfish.

Large aggression gap (6 points) between Frogmouth Catfish and Threadfin Rainbowfish increases stress risk for the more peaceful fish.

In terms of spatial distribution, Frogmouth Catfish prefers the Bottom (Substrate) zone, whereas Threadfin Rainbowfish occupies the Top (Surface) and Middle (Open Water) zones. 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 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: Hyperactive swimmers can stress shy, slow-moving species through constant motion. Aggressive eaters may outcompete shy fish for food, leading to malnutrition.

Worth noting: Frogmouth Catfish is nocturnal and will be most active after lights-out, naturally reducing daytime encounters. Also, Threadfin Rainbowfish 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 6 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 4–12 dGH. Regular testing will ensure conditions stay within this range.

To house Frogmouth Catfish and Threadfin Rainbowfish 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: Sand (Sifters), Leaf Litter/Blackwater, Plants - Densely covered, Plants - Floating. 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.

Frogmouth Catfish and Threadfin Rainbowfish 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. Threadfin Rainbowfish is an aggressive eater that may prevent Frogmouth Catfish from getting enough food.

Because Threadfin Rainbowfish is a fast, competitive feeder, consider using sinking pellets or feeding at opposite ends of the setup to ensure Frogmouth Catfish receives an adequate share.