When predators threaten, the Chromis will disappear in a flash into the coral heads, remaining tucked tightly into the crevices until the perceived danger is no longer present. Other than their schooling behavior and its benefit of "safety in numbers," this is their only means of defense. Although most members will also spend the evening buried into these same coral heads, some species (C. ovalis) will simply lie upon the substrate and adapt a coloration that blends with the sand, most often a mottled gray.
The overall numbers can be confusing to some hobbyists as well. Although "schooling" by large numbers of Chromis is something that can occur regularly, mostly by juvenile fish, this should not be considered commonplace for all adult Chromis. Many, but not all, species prefer to maintain a nest occupied by only themselves or with a small harem of females. Due to the small territories they claim and with their passive nature, unlike most damsels, feeding is done in the close vicinity of their cohorts. Aggregations of these harems, coupled with their profuse abundance on the reef, and their overlapping territories, can easily be confused as a single large school of Chromis. If watched closely, however, members will remain close to the same location, usually within a radius of several meters of their nesting area, and associate primarily with the same members of their harem, even as they forage for food in the water column. When individuals do stray far from home, however, it is always done under the cover of a large school for the purpose of feeding. Schools are a safer option than going at it alone when traveling great distances, and schools can easily overrun single or paired specimens when competing for new feeding grounds. For the species that typically school for the majority of their existence, such as C. atripectoralis and C. viridis, neither nests nor territories are maintained. The only exception to this rule is when spawning occurs. Males of both the schooling species and non-schooling species have similar spawning tendencies.