In the wild, Hydractinia feed on smaller invertebrates found in the shallow mud, however in laboratory environments they are fed brine shrimp.

After a period of darkness, sunlight triggers the rupture of gonadal walls in males and females, causing the release of gametes.

The planula then attaches to a hermit crab shell and subsequently undergoes metamorphosis to turn into a single polyp with extending stolons.

After metamorphosis, the single polyp grows and extends its stolonal network and can reach adult size fairly quickly.

Hydractinia symbiolongicarpus lives in shallow environments along the North Atlantic coast and is primarily found on hermit crab shells.