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When prey contacts a tentacle, only the tentacles attached to the prey contract to bring the prey to the mouth of the gastrozooid. The rest of the colony continues fishing. Gastrozooids work individually or in teams. If the prey is too large to be completely engulfed by a single zooid (e.g. a fish in the case of Physalia), more zooids will be recruited to finish the job. Presumably, the additional zooids are joining the job in response to chemical signals released by the captured prey. Digestion of small prey items such as copepods can be quite rapid: 1–2 minutes (Mackie et al. 1987).

As is the case with other cnidarian groups, digestion of prey is achieved using both extracellular and intracellular mechanisms. It takes place primarily in the gastrozooid, where breakdown of food is accompanied by rhythmic contractions. Particles created during the process of extracellular digestion are taken up via phagocytosis by the endodermal cells of the gastrozooid or, in some cases, can be passed along to palpons via the contractions noted above and taken up there. Further processing takes place in the endodermal cells of both structures. Eventually the cells slough off from the endoderm and disintegrate, allowing the nutrients to be absorbed by the rest of the colony via the stem canal. Indigestible parts of prey are ejected from the gastrozooids the same way they entered, out of the mouth with the help of basal contractions. Palpons expel particulates through a pore in their tip.