African Freshwater Crab Potamonautes obesus

Potamonautes obesus is a robust highland freshwater crab found across East African mountain streams, inhabiting fast-flowing, cool, highly oxygenated rivers and rocky streams from Kenya and Tanzania to Uganda and Rwanda. Its broad, domed carapace and formidable chelae reflect an adaptation to the physical demands of torrential highland waterways.

In captivity, P. obesus requires cooler water temperatures than most tropical freshwater crabs — typically 18–24°C — making it suitable for unheated or lightly heated aquaria in temperate climates. Excellent oxygenation is important, as is strong water movement to replicate the fast-flowing stream conditions of its native range. Rocky substrates with large caves and crevices allow the crab to establish territory.

This species is a fully aquatic territorial omnivore. It is best kept one per tank unless the enclosure is very large with multiple clearly separated rocky territories. A secure, weighted lid prevents escape. Its diet in captivity encompasses sinking pellets, frozen meaty foods, and blanched vegetables, all of which are accepted readily.

Water: 18–24°C, pH 7.0–8.0, GH 5–18, KH 3–12; strong flow and high oxygenation; cooler than typical tropical. Tank: minimum 100 L; large rocky caves, strong current, fine gravel; weighted secure lid; robust filtration. Feeding: omnivore — sinking pellets, frozen bloodworm, mussel, blanched greens, dried shrimp; feed every 1–2 days. Breeding: females brood eggs; fully aquatic juveniles; cool stable conditions required for breeding. Compatibility: one per tank; fully aquatic; predatory on invertebrates and small fish; keep alone or with robust fish.