Fancy Guppies and bacterial diseases

Question
I recently purchased some fancy Guppies for my 15 gallon tank. Years ago, I gave up on them because of some kind of disease, but thought I would try again. I see this disease in mega-pet stores and I don't know what it is. Two females I just got are already infected even though they didn't show signs when I got them 4 days ago. It starts as white patches and then turns brighter white and seems to eat the flesh and turn it white. The fish don't usually make it more than 48 hours after they start showing signs. Its like this stuff makes a circle around the tail area, or looks like a saddle on the top of the fish. What is this and how do I kill it?

Thanks!

Answer
Hi Laura;

It's a bacterial infection known as Columnaris, Flexibacter, Cotton-Wool, etc. It is caused by a gram-negative bacterium called "Flexibacter columnaris". It can be quite devastating and can indeed cause death in a very short time. It commonly affects guppies as well as platies and bettas too. Here are some web pages about it on prevention and treatment;

http://network.bestfriends.org/friends_of_fish/news/5401.html

http://freshaquarium.about.com/cs/disease/p/columnaris.htm

http://www.petfish.net/articles/Bettas/columnaris.php

http://www.cichlid-forum.com/articles/columnaris_disease.php

http://www.aquatic-hobbyist.com/profiles/disease/freshwater/columnaris.html

Good luck...

At Your Service;
Chris Robbins