Steel Blue Killifish

Cyprinodontiformes sp.

Steel Blue Killifish (Cyprinodontiformes sp.) — Easy care, Semi-aggressive, under Livebearer & Killifish. Minimum tank in the app: 21 US gal min; aim for 70–79°F and pH 6.8–8.2. The Steel Blue Killifish is ideal for aquarists who appreciate dynamic schooling behaviour and vibrant colouration.

Steel Blue Killifish (Cyprinodontiformes sp.) in a planted freshwater aquarium
Care levelEasy
TemperamentSemi-aggressive
Min tank size21 US gal min
pH range6.8–8.2
Temperature70–79°F
Max size2.2 in (5.5 cm)
Captive lifespan2–4 years
SchoolingYes · 6+ recommended

Captive lifespan reflects typical experience in a home aquarium, not maximum recorded age; genetics, sourcing, and care vary.

Natural distribution

Americas / Africa (varies)

  • Africa
  • South America
  • Central America & Mexico

Regional colours match the stocking calculator’s origin map.

Steel Blue Killifish Tank Setup

A tank of at least 80 liters should feature ample vertical space and floating plants to simulate their natural habitat. Use soft substrates and create hiding spots to foster security. Moderate water flow and subdued lighting will help them feel more at ease, promoting natural behaviours and reducing stress.

What Do Steel Blue Killifishs Eat?

Omnivorous in nature, they feed moderately quickly, so provide a varied diet to minimize competition and ensure optimal health. Flakes, pellets, and occasional live or frozen foods can enhance their colour vibrancy, but be cautious of overfeeding as this can lead to water quality issues.

Steel Blue Killifish Tank Mates

Best kept with similarly sized, non-aggressive species that occupy different swim zones, such as tetras or rasboras. Avoid mixing them with overly aggressive fish or those that occupy the same mid-level swimming zone, which could lead to conflicts. Ensure they are in groups of at least six to mitigate aggression and promote social stability.

Are Steel Blue Killifishs Good for Beginners?

In App-aquatic we file this under easy care. That still means a cycled tank, realistic stocking, and parameters that do not swing every weekend. Aquarists often underestimate the importance of group size, leading to heightened aggression and stress. neglecting water quality and parameters can adversely affect their health.

Building a community? Run the full list through the stocking calculator before you add anything else.

Log tests and reminders in App-aquatic—free, same data you see here.