Hi, I joined this website to discuss something with my Gymnocalycium mihanovichii. (Moon Cactus). A part of the root stock of my cactus has been turning light green and even a SMALL part of the root stock has been "decaying". I wish I could upload an image of it but currently I'm not where I live. All I have is a picture of the head. Here.
I've had this for about a year, any help? Also I'm watering it once a month and giving it PLENTY of light.