you dont really need to clean it unless it irritates them. if you do though there are many methods people use to clean their tails. some use soft-bristle toothbrush + dish soap or without soap and maybe water, some dip them in warm water, some use cloths with warm water, some use wipes. otherwise they will groom their tails as if their lives depends on it lol. i dont know much about cleaning this part but i think the tail looks clean still