[Delphinus]

I think a "red tide" is basically the same thing. (??)

I really wish I could point at something I did wrong or some kind of parameter that was out of whack, but, I can't really conclusively think of anything. I know that the first time was shortly after a huge sandbed disturbance, but there was no such event the second time (that I can think of). I wish I could impart more "lessons learned", sorry.. all I know is both times it finally seemed to subside after about a week of no lighting. I got lucky on the second time in that it went away without me turning my actinics off. Mind you, there was a move involved too, so maybe the second huge-sand-disturbance somehow contributed to knocking it back.