columanaris is absolutely devastating as I lost 21 fish, I haven't seen images of what the op called fluff I just see what looks like fin and tail rot, unless that's what they are talking about, but bacteria in fish is the same as in humans just a bit different, as that's why they tell you to keep your house under 70° because bacteria grows more slowly if it even grows or worsens at all, your graph just means that the fin and tail rot "can start growing at that temp" it does not mean that it nessessarily slows down at increased Temps as bacteria in all aspects good and bad grow faster and spread faster at higher Temps , water changes are more important than temp In this case