My Congo tetras have this extremely annoying habit of biting the tips of my Anubias Nanas and only the Nanas, however I only have another Nana petite which they don't bother. Has any one ever seen this!? How can i get these buggers to stop? I don't want to get rid of them but they may leave me no choice. Maybe something that is done in their natural habitat? Any help will be great. By the way they get fed plenty and yes I have caught them in the act!