Feeding
Mettam (1980) found that Aphrodita aculeata was an active predator feeding primarily on other worms, including both large active polychaetes and sedentary polychaetes. For example, the gut contents of Aphrodita aculeata were reported to contain the remains of Pectinaria and Lumbriconereis; polynoids, nereids, sabellids and terebellid polychaetes; nemerteans, and very young crabs and hermit crabs. In laboratory experiments, Aphrodita aculeata did not feed unless buried and only attacked prey overnight. In the laboratory it fed on Nephtys hombergi, Hediste diversicolor and Nereis virens. Prey was swallowed whole, head first, passing slowly into the intestine, and its remains being deposited in a faecal pellet in the same order, i.e. head first (Mettam, 1980). Swallowing large prey is a laboured process (Mettam, 1980), e.g. the king rag Nereis virens, is about three times the length of the sea mouse. The swallowing of Nereis virens by the sea mouse was likened "to a hedgehog swallowing a snake" (Gunnar Thorson pers comm. cited in Mettam, 1980).

Commensals
Aphroditoidea are known to harbour a variety of organisms under their scales and chaetae. Aphrodita aculeata was reported to host several entoprocts, e.g. Loxosomella claviformis, Loxosomella fauveli and Loxosomella obesa (Chambers & Muir, 1997).