Yes they can... will they? Is a completly differnt story.. Clown fish are odd its instinctive for them to do it but somtimes it just never happens, and from what i have read there is nothing you can do to help pull that instinct out in them. Mine have just started, but it has taken a while and they still are not fully "hosting" yet. But I have heard that 1 day to 1 year is not uncommon..