sick mollies

Question
Hi, I have 7 dalmation mollies and an algae eater. one of the mollies has a fluffy white patch on the side of his head. He also has a hole in th middle of his head just above his eyes. It looks like something has been eating on him. I had a fish with the same symptoms ,only worse, die last night. Please help me.

Answer
Hi Mary
What's the tank size?  

From what you described, I would say it sounds like a columnaris infection.  It's a bacterial infection-can be treated though.  I would recommend an antibiotic like Maracyn Two.  Be sure you're doing frequent water changes, weekly of 25% assuming the tank is not overstocked.  Don't add any new fish for awhile either.  

Here's a link that explains a bit more what columnaris is, and it has some photos:

http://www.flippersandfins.net/flexibacter.htm


Good luck!

Christy