Pseudotropheus johannii, commonly known as Johannii or Bluegray Mbuna, is a vibrant and active species of cichlid from Lake Malawi in Africa. This species is well-loved in the aquarium hobby for its striking coloration and dynamic behavior, making it a popular choice for those who keep African cichlid tanks.

The Johannii exhibits sexual dimorphism in its coloration. Males typically display a deep blue or blue-gray body with black bars and a hint of yellow or orange on the dorsal fin. Females and juveniles, on the other hand, are usually orange or yellow throughout, making them just as visually appealing but in a different color palette. This color differentiation makes it easier for aquarists to identify the sexes within their tanks.

In terms of aquarium care, Pseudotropheus johannii requires conditions that mimic the rocky shores of Lake Malawi. The aquarium setup should include plenty of rocks and caves to provide hiding spots and territories, which are essential to mitigate aggression, a common trait among Mbuna cichlids. The substrate should consist of sand or fine gravel, and the tank should have areas of open water for swimming.

Water quality is critical for maintaining the health of Johannii. The water should be alkaline with a high pH and hard water conditions, typical of their natural lake environment. Efficient filtration is required to manage waste and maintain clean water, and regular water changes are essential to keep water parameters stable.

The diet of Pseudotropheus johannii should be carefully managed to avoid health issues such as bloat, which can be common in Mbuna if fed an improper diet. They are primarily herbivores, and their diet should consist mostly of plant-based foods. High-quality cichlid pellets or flakes formulated for herbivorous fish, supplemented with spirulina, vegetables like zucchini and spinach, and the occasional treat of live or frozen foods, should keep them healthy and vibrant.

Breeding Johannii can be quite rewarding. They are mouthbrooders, with females carrying the fertilized eggs and fry in their mouths for several weeks to protect them. Setting up a breeding tank with optimal conditions and minimal stress can encourage spawning.

Overall, the Johannii offers a mix of beauty, intriguing behavior, and a moderate care challenge. While they can be aggressive, proper tank management, adequate space, and compatible tank mates can mitigate most issues, making them suitable for aquarists with some experience in keeping African cichlids. Their striking appearance and fascinating behaviors make them a standout addition to the appropriate setup.