ABSTRACT: Coral reef cnidarians often host crustaceans in multi-level symbioses that may cause reef-wide impacts, especially through anemoneshrimp cleaner interactions with fish clients. Despite the ubiquity and importance of these interactions, patterns of temporal and spatial variation in crustacean association with sea anemones remain largely unknown. We censused corkscrew sea anemones Bartholomea annulata and crustacean associates (5 shrimp and 1 crab species) every 3-6 mo for 2.5 yr at 2 reef sites in St. Thomas, US Virgin Islands. Crustacean abundance per anemone varied with species and census period. Occupancy rates increased with anemone body size, more so offshore where anemones were smaller and less abundant than inshore. Four species of obligate anemoneshrimps partitioned space among 5 microhabitat zones on the host anemone body. Dynamic multi-state models revealed that anemone persistence was enhanced primarily by anemone body size, with variable secondary effects of site and anemoneshrimp species. The presence of the snapping shrimp Alpheus armatus did not enhance the persistence of host anemones. However, the presence of the dedicated cleaner shrimp Ancylomenes pedersoni enhanced the persistence of small host anemones at the inshore site but reduced the persistence of the occasional cleaner shrimp Periclimenes yucatanicus on host anemones, indicating mutualistic and competitive interactions among some partners in this system. Patterns of association among anemones and crustaceans varied significantly at both temporal (seasonal and annual) and spatial scales (among anemones and reef sites), with implications for the ecology of client fishes that visit these Caribbean anemones to receive cleaning services from anemoneshrimps.