What Causes Popeye?

[aloaring]

Hey guys. i was hoping somebody could help me.
I have 3 female bettas in a 15 gallon planted tank with a shoal of neons. Water paramteres have been tested by my LFS and seem fine. 9 months ago one of my girls got popeye and lost an eye she still feisty and has a happy life and all the other fish were fine. But now 9 months later another of my females has popeye i've seperated her and am treating her with melafix. But i'm confused as to why it has happened again so does anybody know the causes of popeye? Cause it looks like i'm goign to end up with 2 one eyed fish !!

 

[lisie]

Popeye is a bacterial infection caused by poor water quality. Isolate the female with popeye (for her own safety and so you're not medicating the other fish), add Maracyn 2, and keep the water very very extremely clean.

Water changes more often in that tank is also a good idea. It's easier to prevent this stuff from happening than it is to treat it.