Blue Pearl / Nigripinnis Kilifish is one of the strangest fish for your aquarium. It is a species of killifish from the Rivulidae family. This species is widely found in the Lower Parama and Uruguay river basins in South America. Their overall color ranges from light blue-gray to dark gray, and the fin has dark colors with blue spots. Females are lighter than the male. Males usually possess a blue-black body color that extends into their fins. This species is sensitive and requires frequent water changes in captivity. They need cooler water with an optimal temperature of around 20-21 °C. The…