A unique case of triple symbiosis between a goby, a pistol shrimp, and a porcellanid crab sharing the same burrow close to reef patches in Lembeh Strait, Indonesia, is described from direct observations for the first time. The burrow, typically occupied by shrimps and gobies, is shared with the porcellanid Enosteoides lobatus. In the goby-shrimp association, the fish inhabits the burrow, which is constructed and kept clean by the shrimp, and the fish warns the shrimp of potential dangers approaching their refuge. The porcellanid lives in the burrow and also benefits from living in a habitat where it could not survive without the two sentinel species. Because the limiting resource for the suspension-feeding porcellanid is protected space, this liaison is an adaptation by E. lobatus to a symbiotic life in a habitat that protects it from predation, and is optimal for filter feeding.