Doctor Phlox's osmotic eel was a female, and he offered to give her to E'Lis, a doctor on a deuteriumminingcolony in 2152, but she joked she wouldn't know what to feed her. Phlox then explained to E'Lis that the eel's feeding needs were relatively modest, as it only required a nutrient broth every three or four days. He further noted that while they were working, they required their nutrient broth even less, as they usually ingested a little blood while healing an injured artery. (ENT: "Marauders")
The fictional use of an osmotic eel for medical purposes echoes, in reality, the use of leeches on wounds, hundreds of years ago.
When it came time to design the osmotic eel, the task fell to Makeup Supervisor Michael Westmore, because the eel was supposed to be alive. He later noted, "They just said, 'You do the leech!'" Westmore produced numerous sketches, from which the producers chose the final, starfish-shaped design. The prop of the creature was then manufactured in the makeup lab, again due to it being supposedly alive. The model was created complete with hairs but required an extra small detail for its on-screen appearance. "We had it all goo'd up; there was stringy goo on the bottom, so when it was picked up those little stringy things would hang down," Westmore explained. Between its appearances in Star Trek: Enterprise, the model was placed into his desk drawer. (Star Trek: The Magazine Volume 2, Issue 7, p. 112)