Well, unfortunately the rot is already back... argh!
I changed his water out (removed the antibiotic) last Thursday night, and by Saturday morning (when I had planned on doing a partial change anyway) his dorsal fins were receding and blackened at the tips. This was the fin that previously was not affected, but it is the fin that he either tore off or bit off while I was away Labor Day weekend. Just 36 hours out of the antibiotic caused this... kind of infuriating!
Anyway, otherwise he seems fine: he's active and eating. I did put more of the maracyn 2 in his tank, to hopefully nip this in the bud. I also ordered online (couldn't find it in any stores near me) the API triple sulfa. That's supposed to arrive tomorrow and I'm going to give him a course of that. I'm thinking maybe the rot was advanced enough that the standard week-course of the M2 was not enough, OR perhaps there is some other type of bacteria that the M2 is not effective against...
Can you remind us , is it second course of the Maracyn you doing?
Would you able to show close picture of his dorsal?
Yes, this is the 2nd course of the Maracyn 2. I just tried to get some pictures, but he is way too active right now (a good sign I guess), and he hates the flash (I shone the flashlight to check the rot and he doesn't like that either).
Basically, on Saturday the tips of his dorsal fin were beginning to blacken and recede. It looks a lot like the textbooks cases of fin rot I have seen pictures of online. After just 24 hours in the M2 his dorsal fin actually looked better. As of Sunday night the blackened edges were less, though it is still ragged looking.
I am thinking maybe the first course of M2 just wasn't enough to knock out the bacteria?? Or possibly different bacteria involved?
Thanks for asking. He is doing fairly well, but not great. His behavior is good and he is eating, but his fins (specifically his pelvic) still look ragged, black and terrible (imo). His dorsal fin looks better since I did another course of the antibiotics (which ended yesterday).
Here is what he has had so far for treatment (other than very clean water, which I have been changing 100% every day or every other day):
2 weeks of 100% water changes daily and aquarium salt, which did absolutely nothing to help him.
1 course of Maracyn 2, lasting 5 days (big improvement with this)
36 hours in clean, unmedicated water and the fin rot came back
2 days more of Maracyn 2, then I switched to API Triple sulfa (waiting for order to arrive in mail)
1 full course of API TS (4 days total, per instructions, mild improvement)
100% water change.
So now he is on clean, unmedicated water that I treated with Seachem Prime.
I plan on monitoring and doing at least 1 50% water change and 1 100% water change per week, as long as he does not worsen. He is in a 2-gallon, unfiltered, heated (~78 degrees F) container. He seems to do better without the filter current.
Here are 2 pics. One is a closeup of a pic I posted previously (his pelvics still look pretty much the same), and another recent closeup. Sorry about the size and the second one is kind of poor. I stink at fish pics, lol.
The rest of him looks pretty much fine right now. His dorsal and tail fin tips are a little curled and torn-looking, but their color is fine.