Can Green Spotted Puffer (Brackish) and Rachov's Killifish (Annual) Live Together?

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

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

Green Spotted Puffer (Brackish) and Rachov's Killifish (Annual) both frequent the Middle (Open Water) and Bottom (Substrate) 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: Shrimp eaters may also prey on very small nano fish.

Worth noting: Rachov's Killifish (Annual) 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.

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 12–12 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. An aquarium test kit is recommended for monitoring.

To house Green Spotted Puffer (Brackish) and Rachov's Killifish (Annual) together, plan for an aquarium of at least 137 litres with a minimum length of 80 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), Shells (Breeding/Hiding), Soil / Nutrient Rich, Leaf Litter/Blackwater, Plants - Densely covered. Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Green Spotted Puffer (Brackish) requires Sand (Sifters), while Rachov's Killifish (Annual) requires Soil / Nutrient Rich. These substrate types may be difficult to provide simultaneously. Compromise where possible or prioritise the more critical need.

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