they will grow back the head but it does take time. keep an eye on him and you will see a very small head start to form . the only bad thing is that the new head is very rarely as big as the original. keep an eye on that duster too. they require a lot of nutrients in the water colum to survive. most of the time they slowly starve to death. you can also try target feeding him once a week. just make sure you turn all of the current off in the tank. but good luck with him. I would love to keep one I am just afraid of him dying.