Can Rachov's Killifish (Annual) and San Juan Cory Live Together?

Rachov's Killifish (Annual) is a generally mild-mannered species (3/10), while San Juan Cory is peaceful (0/10). This modest difference means Rachov's Killifish (Annual) may occasionally assert dominance over San Juan Cory.

Rachov's Killifish (Annual) and San Juan Cory both frequent the 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.

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 22°C and 26°C. Aim for the midpoint of this range (around 24.0°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 Rachov's Killifish (Annual) and San Juan Cory together, plan for an aquarium of at least 60 litres with a minimum length of 60 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: Soil / Nutrient Rich, Leaf Litter/Blackwater, Plants - Densely covered, Sand (Sifters), Smooth Gravel (Sensitive Barbels). Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Rachov's Killifish (Annual) requires Soil / Nutrient Rich, while San Juan Cory requires Sand (Sifters). These substrate types may be difficult to provide simultaneously. Rachov's Killifish (Annual) requires Soil / Nutrient Rich, while San Juan Cory requires Smooth Gravel (Sensitive Barbels). These substrate types may be difficult to provide simultaneously. Compromise where possible or prioritise the more critical need.

Both species do well with low (still water) water movement, so a standard filtration setup rated for the tank volume should suffice.

This pairing usually fails when the tank is treated like a standard mixed community and the caution flags are ignored. Rachov's Killifish (Annual) and San Juan Cory need extra room, more cover, and closer observation during the first few weeks so small aggression, feeding, or territory issues do not snowball into a long-term problem.