Tanganyika Crabs (Platythelphusa spp.): Expert Care, Diet, and Breeding Guide

The Tanganyika crabs, belonging to the genus Platythelphusa, are among the rarest freshwater crustaceans kept in aquariums. Because of their limited distribution in Lake Tanganyika and the scarcity of comprehensive studies, information on their biology is often incomplete. This guide compiles the latest scientific data and practical experience to help experienced aquarists successfully keep and breed these fascinating crabs.

Quick Reference

• Common name: Tanganyika crab (African crab)
• Scientific name: Platythelphusa spp.
• Recommended tank size: 10‑gal (≈40 L) for a single adult; smaller species can be housed in 5‑gal tanks.
• Environment: Freshwater, fully aquatic
• Temperature: 77–81 °F (25–27 °C)
• pH: 7.0–8.5
• General hardness (GH): 10–20 dGH
• Carbonate hardness (KH): 7–10 dKH
• Nitrate: <20 ppm
• Diet: Omnivorous – 20–30 % protein
• Behavior: Nocturnal, territorial, non‑burrowing, aggressive toward conspecific males
• Longevity: 3–5 years in captivity (maximum unknown in the wild)
• Color: Brown to grey with species‑specific markings
• Breeding: Difficult; requires mature, well‑stabilised conditions

Taxonomy and Species Overview

Initially grouped under the family Potamonidae, the African freshwater crabs have been reclassified into the family Platythelphusidae (Cumberlidge, 1997). Within Lake Tanganyika, nine valid species have been documented:

1. Platythelphusa armata – Least concern (IUCN)
2. Platythelphusa conculcata – Least concern (IUCN)
3. Platythelphusa denticulate – Vulnerable (IUCN)
4. Platythelphusa echinata – Least concern (IUCN)
5. Platythelphusa immaculata – Near threatened (IUCN)
6. Platythelphusa maculata – Least concern (IUCN)
7. Platythelphusa polita – Least concern (IUCN)
8. Platythelphusa praelongata – Vulnerable (IUCN)
9. Platythelphusa tuberculata – Least concern (IUCN)

These species differ in carapace shape, spine arrangement, and habitat depth. Notably, P. armata is the largest, with a carapace up to 2.5 in (6.5 cm) and powerful chelipeds suited for mandating gastropods.

Natural Habitat

All Platythelphusa species are endemic to Lake Tanganyika, the world’s oldest (9–12 Myr) and deepest Rift‑Lake (1470 m). They inhabit rocky littoral zones, occupying depths from 5 m to 160 m depending on the species. Substrates are typically cobbles, boulders, or fine sand, providing crevices for shelter and for propitious hunting.

Physical Characteristics

All species possess a subhexagonal carapace that is broader than long, with coloration ranging from muted brown‑grey to mottled patterns of yellow, green, or reddish‑brown spots. Notable adaptations include:

• P. tuberculata and P. praelongata have elongated, slender legs for efficient movement through mud.
• P. maculata is small and rounded, enabling it to occupy gastropod shells.
• P. conculcata and P. immaculata feature flattened carapaces that allow access to narrow rock fissures.
• P. armata bears enlarged chelipeds for crushing heavily calcified snails.

Diet and Feeding Behavior

In the wild, Tanganyika crabs are opportunistic scavengers: algae, cyanobacteria, diatoms, detritus, and small invertebrates such as snails and fish eggs. P. armata shows a preference for mollusks. In captivity, a balanced diet of high‑protein foods (e.g., frozen blood worms, brine shrimp, krill) combined with vegetable matter (leafy greens, frozen algae) supports healthy growth.

Feed 3–4 times weekly for adults and daily for juveniles. Allow 12–24 h for uneaten food to decompose; discard any leftover to prevent water quality degradation.

Behavioral Notes

• Mandate a tight‑fitting lid; crabs can inadvertently fall out of the tank.
• Non‑burrowing; may perform shallow horizontal burrowing into debris during temperature extremes.
• Not socially tolerant: keep one male with one or two females to reduce mandra aggression.
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