Can Otocinclus and Rachov's Killifish (Annual) Live Together?

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

Otocinclus 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: Hyperactive swimmers can stress shy, slow-moving species through constant motion.

Worth noting: Rachov's Killifish (Annual) is a known jumper, so a tight-fitting lid is essential.

To improve the chances of a peaceful coexistence in this community tank: 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 21°C and 26°C. Aim for the midpoint of this range (around 23.5°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. An aquarium test kit is recommended for monitoring.

To house Otocinclus and Rachov's Killifish (Annual) together, plan for an aquarium of at least 46 litres with a minimum length of 45 cm. This accounts for the larger species' space requirements with an additional 20 % buffer to reduce territorial tension.

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: Established Algae (Otocinclus), Plants - Densely covered, Smooth Gravel (Sensitive Barbels), Driftwood (Digestion/Hiding), Soil / Nutrient Rich, Leaf Litter/Blackwater. Meeting these requirements will help both species thrive.

Note a potential conflict in setup requirements: Otocinclus requires Smooth Gravel (Sensitive Barbels), 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.