In a 24 gallon aquapod, I have a nice small field of green stars, and a green bubble that until three days ago was huge, healthy and well-fed. On tuesday, I noticed that the bubble and my green stars had shrivelled up to almost nothing. Nothing seemed to be wrong with any of my fish or other livestock. I replaced the blue lights in my tank (sorry for the non-technical descriptions), and the green stars have started to come back, but the bubble is still shriveled very tightly. I've tested the water and that is fine, and, as I said, the fish and my other livestock (polyps, anemone, zinnea and shrooms) seem to be unaffected. Does anyone have any ideas? Thanks.