Vampire Crab Geosesarma hagen

Geosesarma hagen is a Javan vampire crab described relatively recently, displaying deep violet-purple to near-indigo carapace colouration with the vivid contrasting yellow eyes characteristic of the genus. It originates from the humid lowland and coastal forest habitats of Java, Indonesia, where it inhabits areas close to small streams, seeps, and wet rocky surfaces.

Like its congeners, G. hagen is semi-terrestrial and requires a paludarium setup that prioritises the land component, with only a shallow water section. The substrate should be kept consistently moist with tropical soil, sphagnum moss, and leaf litter to replicate the forest floor conditions of its native habitat. Hiding places such as cork bark, coconut shells, and dense moss clumps are essential.

G. hagen is a direct developer — females carry a small clutch of eggs that develop directly into miniature crabs, bypassing a free-swimming larval stage. This makes captive breeding straightforward for prepared keepers. Groups can be kept with a single male and multiple females to reduce male-to-male aggression. Diet is varied and includes dried insects, fruit flies, blanched vegetables, and small sinking pellets.

Water: 23–28°C, pH 7.5–8.0, GH 6–15, KH 3–10; shallow water section, dechlorinated only. Tank: minimum 30 L paludarium, moist tropical soil substrate, dense moss, cork bark hides, secure ventilated lid. Feeding: omnivore — fruit flies, dried insects, blanched greens, sinking pellets, leaf litter; feed every 1–2 days. Breeding: direct developer; female broods small clutch; juveniles are miniature adults; separate from other males. Compatibility: keep as a group of 1 male and 2–4 females; incompatible with fish; avoid mixing with competing crab species.