Actiniidae is the largest family of

Actiniidae is the largest family of sea anemones. Members of this family are typically those anemone found along shorelines.
Actiniidae can be identified from other anemone by the number of tentacles. Actiniidae have only one tentacle per space between mesenteries and the mouth of the anemone. Mesenteries are double layers of peritoneum connecting various components of the abdominal cavity.
Another defining characteristic of this family, is that they do not form symbiotic relationships with fish, with the exception of the "Bubble-tip anemone" or Entacmaea quidricolor. Some forms of anemone protect fish from predators in return for food. Meaning that they feed off of the food particulates that fall off the fish, or are cleaned off by the fish