We noticed yesterday that it was lying on the filter outlet (which sits under the water, with several holes for the water to come out), which is not unusualy as they’ve done this before; except that he was a bit sideways, and breathing quickly. Looking at him closely, there appeared to be something behind his dorsal fin – whether loose scales or something growing there, I don’t know; his tail also seemed to have something on it, making it a bit opaque, but whether that was real/unusual or I was paranoid, I don’t know. Anyway, we moved him to the qt, in an effort to save the others really, and he died a few hours later. I think the others are okay still.

As well, two of the mollies seem to have black lips! I’m not sure whether to worry or if it’s a result of their eating the black alagae on the tank walls. It looks pretty funny. [Later note: it was from the algae.]