So my wife and I woke up this morning to find our betta Fred dead in the water. I don't know what it is, and although slightly different, this is the closest thing we could find, especially the speed of it.
Last night at around 2330 I noticed a dark grey/black spot about an 1/8" diameter under the front of his dorsal. By 0200, when we were going to bed, it had grown to 1/4" and I noticed it had a ring of white surrounding it. I was going to do a 50% tank change this morning, but when I woke up at 1100 I found him floating. Still want to do the research on this. He was a blue betta, had him for about 6 months from PetCo, usually very active though last night was hanging out by the water intake, wouldn't even come up to his feed hole last night. Lightly tapped next to him and barely moved last night. I had just done a 100% water change on Thur and today was supposed to do a 50% today. I'll attach some pictures as well to give a better look, just not sure what it is or how it happened. The main thing is the speed of it seems like what is being talked about here, just a few small differences, like the ring of white and not starting at the fins.