Fin Rot being the closest description I've got in my arsenal. Besides the tail, the lower body fins are also fraying.
You can try the trick of setting up your phone to video the tank when you leave the room. You might catch a culprit that way. Still, a bite only takes a split second and there are lots of seconds in a day!
Unfortunately I can't answer that. I was out most of the weekend and just noticed the fin today. The last time I know it was not notched was last week.
Yes - thats why I tagged Jay to comment. Fin rot also (in my experience) does not go away immediately after treatment. - I meant to mention - is it possible its related to an ammonia spike?
would a fin regrowing over a course of call it 3 weeks be considered immediate?
It could be both issues - tankmate aggression, followed by a bacterial infection that eats away at more of the fin tissue. Fin rot, as a disease, is almost never a primary disease, there is always some physical issue that gets it starts - a bite, tail abrasion, etc.
Thanks Jay. All these fish will be back in the dt within 10 days. What action would you advise I take for this guy?
If possible a broad spectrum, gram negative antibiotic will help reduce the issue of infection. This should be done in a treatment tank though. If it was minor damage, I’d just say let it heal on its own, but there is a good chunk missing. If the hypural bone gets infected, the fin section may not grow back.
