Can Green Spotted Puffer (Brackish) and Lyretail Killifish Live Together?

Green Spotted Puffer (Brackish) is a highly aggressive species (9/10), while Lyretail Killifish is generally mild-mannered (3/10). This notable difference means Green Spotted Puffer (Brackish) may occasionally assert dominance over Lyretail Killifish.

Large aggression gap (6 points) between Green Spotted Puffer (Brackish) and Lyretail Killifish increases stress risk for the more peaceful fish.

Green Spotted Puffer (Brackish) and Lyretail Killifish both frequent the 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.

Additional behavioural considerations to keep in mind: Aggressive fish may bully and stress shy, slow-moving species. Shrimp eaters may also prey on very small nano fish.

Worth noting: Lyretail Killifish is a known jumper, so a tight-fitting lid is essential.

The safe temperature window for both species falls between 24°C and 26°C. Aim for the midpoint of this range (around 25.0°C) for optimal comfort.

The pH requirements of Green Spotted Puffer (Brackish) (7.5–8.5) and Lyretail Killifish (5.5–7) do not overlap, making it impossible to satisfy both species simultaneously.

Hardness requirements are incompatible: Green Spotted Puffer (Brackish) needs 12–30 dGH while Lyretail Killifish requires 1–10 dGH.

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 Green Spotted Puffer (Brackish) and Lyretail Killifish together, plan for an aquarium of at least 114 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), Shells (Breeding/Hiding), Plants - Densely covered, Plants - Floating, Leaf Litter/Blackwater. 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.

Green Spotted Puffer (Brackish) and Lyretail Killifish 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. Green Spotted Puffer (Brackish) is a known shrimp eater and may prey on small invertebrates or nano fish like Lyretail Killifish.