[Delphinus]

Definitely has a "spent" look to it today (I went home at lunchtime to check on it). Not completely deflated but much smaller than usual.

I wonder if this might not be the first time it has happened, just that this is the first time I witnessed it. Twice before in two years I have found the anemone deflated, once when the water was cloudy, but at the time I thought it might have been a caulerpa sporulation (but I was never able to confirm that). Of course, it's just speculation.

The water was realllly stinky so I'm worried about fouling. Still is a little, actually, although filter floss and the carbon have done a wicked job of polishing the water clean already. Nobody else seems to be affected, so so-far-so-good. I'm going to make a new batch of SW so I can do a big water change (tank is due for one anyway, so what the heck).

...
Dinoflagellates? What a pain. I could not get rid of them when I had them back in December/January. Only thing that worked was I turned my tank lights off for almost a week. After almost a week of no lights I had to scale back the photoperiod and very slowly ramp back up to the normal photoperiod, so in actual fact it's more fair to say the photoperiod was knocked back almost 3 weeks in an effort to get rid of the dinos. But it worked. Nothing else did, unfortunately. Good luck getting rid of them, let me know how it works out and what you try (I'm always afraid they're going to come back).