The unusual title of this thread caught my eye. Usually people complain that their zoos won't OPEN, not that they won't CLOSE! :lol:
I think we've got two issues going here, "umbrella syndrome" and closing in general.
IMHO, umbrella syndrome seems to be a sign of stress or discomfort, but can often pass without apparent or obvious effort or changes. And just to be clear, what I mean by umbrella syndrome is when it looks as though someone has pulled the skirt down on a given polyp such that the polyp assumes an umbrella or mushroom shape with the mouth and oral disk bulging upwards and the skirt looking peeled back or drooping.
And while umbrella shapes polyps do often recover, I've also seen them not recover, become very thin stalked and eventually melt.
It would be awesome if we could come up with what we think the cause of umbrella syndrome is and how to keep it recoverable instead of the first step towards eventual melting.
Grandis has offered up some good theories and I'd lean towards an environmental cause as well (water, flow, light, etc.). Could also be a reaction to internal infection or a parasite, though the parasite paradigm doesn't seem to fit my observations.
Any other thoughts?
