Lamprologus ocellatus (a.k.a. Neolamprologus ocellatus) one of the very small shell dwelling cichlids from Lake Tanganyika.
The water of the Lake is so hard and alkaline that the Neothauma snails develop very thick shells, which do not dissolve after the snails dies (which usually happens in freshwater). They accumulate in depressions in the lake floor and these little cichlids hide inside them.
When I kept cichlids I bred hundreds of them - they are probably my favourite aquarium species, as they are attractive, cute and just as feisty and interesting as any of the larger cichlids.
