I have a female guppy that just beat up and killed another female guppy. She attacked and beat the other guppy to the sand before I could fish her out and save her. Have you ever heard of such a thing? It happened during feeding time and she did not want to share any of the food. Oh well all I can hope for is that she will drop a few fry to re-populate the tank, and that she does not eat the fry.
