Unknown it seems. I've read conflicting findings. Well, not conflicting so much as different. Some say its a seasonal thing in the wild. Or fresh water from rains. Some say iodine depletion. Some say because you can have too much densely packed in where if suffocates in its own mucus.
Just as much is the mystery about why some pump and others don't. Why pumping in one tank, yet ceasing to pump in another.
My leading candidates for crash were most likely being too dense in my tank. Or better yet, I hadn't done a water change in about 3 months - maybe lacking iodine from the fresh salt water mix - which again are not conclusive.
But, I did just read xenia being described as a Pheonix. Forgot what month, but TFH mag has an article talking about xenia crashing and rising again. Most tear it all out of the tank, which I did. The article went on to say that that wasn't necessary. Fluff got to me too late - after my panic attack. If dead, it turns into a jelley like substance. When crashing, just gets brown and weak looking. Still, I needed to thin out anyway. I've got maybe 5% of what I used to have, both elongata and pom pom. The LFS
and Fluff, who got some the morning I noticed someting strange both have xenia still looking alright. My crisis seemed to happen w/in a 24 hr period.
My zoos don't look as bad as they did yesterday, but they aren't opening. Still encouraging.