Tanganyikan shell-dwellers

On the sand beds of Lake Tanganyika, far below the rocky shoreline, lie graveyards of the snail Neothauma tanganyicense — millions of empty shells accumulated over millennia. A group of small Lamprologine cichlids has evolved to live in nothing else. They shelter in the shells, lay their eggs deep inside them, and in some species never stray more than a body length away. Neolamprologus multifasciatus, at roughly 1.5 in, is among the smallest cichlids known — a fish that defends a territory measured in centimetres.

That tight bond with a single object makes the shellies unusually rewarding to keep: a colony will excavate the sand, arrange and re-bury their shells, and breed almost continuously, all within a footprint a larger Tanganyikan would barely notice. They ask for the lake's water — hard and distinctly alkaline, around pH 8.5–9.0, in the mid-20s °C — and a deep bed of fine sand with more empty shells than fish, so every adult and maturing fry has a home to claim.

This is the atlas's water-first story in miniature: a whole way of life dictated by one lake's chemistry and one snail's shell. Each species below links to its full profile, Tanganyika distribution and water tolerances; the lake itself is worth reading alongside them.