Fin rot on neon tetra? Next steps for treatment?

Not an emergency, per se, but definitely something I've been concerned about.

When I moved this tank and its inhabitants a few weeks back, I noticed one of my neon tetras had sustained an injury to its tail fin. I wasn't terribly worried at the time, since I've had a neon injure a fin in the past and it healed perfectly on its own. However, the fin on this guy started developing this white, slightly ragged edge on the lower part. I know fin rot is a very common misdiagnosis, but to my eye, this looks very similar to how fin rot manifests in neon tetras. The fish is very active and is eating and pooping normally.



I started out by treating the tank with salt at 1tbsp/5gal for one week. That didn't seem to do anything, so I increased the dose to 2tbsp/5gal for another week. That also didn't seem to do anything, so now I'm working through a series of daily ~20-25% water changes to remove the salt, and I'm hoping that the daily water changes will also help with healing. I normally do 50% water changes every week and heavily over-filter, so my water is generally very clean anyway. The rot hasn't really progressed, but it hasn't gotten better either.

While I'm hoping the daily water changes lead to an improvement, I'd like to get a sense of next steps in case they don't. I do have some doxycycline (API Fin & Body Cure) which I could use. It's my last resort option since it would require catching the fish and setting up a treatment bucket, but I'll definitely use it if necessary. I also have methylene blue, but I know it's more effective for fungus than bacteria. Is there anything else I could do? I don't really want to go back to salt treatments since they didn't help and I think the plants did not appreciate it. How long should I continue the daily water changes? I was planning on starting out with a week's worth and seeing where that gets me. I just completed the third water change today.

Ammonia: 0ppm
Nitrite: 0ppm
Nitrate: ~5ppm
pH: 6.6-6.8
Temp: 74F

It looks like excess mucous but could be fungus, (I'm more inclined to think its mucous). Salt should have stopped it if it was fungus.

It's not bacterial because there is no red in the area.

Doxycycline is an antibiotic that wipes out filter bacteria and should only be used on known bacterial infections. Keep the medication in its packet for the time being.

You can try Methylene Blue. It treats bacteria and fungus and will wipe out filter bacteria and turn silicon blue, but it's quite safe for fish. You can use Methylene Blue while there's salt in the water so you don't have to get all the salt out before you treat the fish. I would recommend treating it in a separate tank/ container if you use Methylene Blue or Doxycycline.

Colin_T said:

It looks like excess mucous but could be fungus, (I'm more inclined to think its mucous). Salt should have stopped it if it was fungus.

It's not bacterial because there is no red in the area.

Doxycycline is an antibiotic that wipes out filter bacteria and should only be used on known bacterial infections. Keep the medication in its packet for the time being.

You can try Methylene Blue. It treats bacteria and fungus and will wipe out filter bacteria and turn silicon blue, but it's quite safe for fish. You can use Methylene Blue while there's salt in the water so you don't have to get all the salt out before you treat the fish. I would recommend treating it in a separate tank/ container if you use Methylene Blue or Doxycycline.

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No, it's not mucous. It doesn't look like excess mucous in person. The lower lobe of this neon's caudal fin is shorter than the upper lobe, which indicates to me that it is indeed actually rotting.
And, respectfully, just because the site isn't red, doesn't mean it isn't a bacterial infection. Basically everything I've read about fin rot has said that it is almost always bacterial (occasionally fungal, often as a secondary infection) and that in fish with clear fins, it very often manifests as a white, ragged edge to the fin. Sometimes there's red, but not always.

If I do treat with medication in the water, it will be in a separate container.

Seisage said:

If I do treat with medication in the water, it will be in a separate container.

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I agree, I would try KanaPlex too

Fishfunn said:

I agree, I would try KanaPlex too

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I might, as a very last resort. I hear people have had luck with it for very advanced fin rot, but kanamycin doesn't appear to target any of the bacteria that commonly cause fin rot. It's also a very powerful antibiotic in general. In humans, it's generally only used for very serious bacterial infections.

Seisage said:

I might, as a very last resort. I hear people have had luck with it for very advanced fin rot, but kanamycin doesn't appear to target any of the bacteria that commonly cause fin rot. It's also a very powerful antibiotic in general. In humans, it's generally only used for very serious bacterial infections.

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Yeah, cured tail rot with antibiotics before. I am thinking one fish might have nipped the tail and some bacterial infection set in. With an infection like that usually one dose does the trick. The directions say no more than 3 doses, but 1 would clear it right up. Other than trying salt and methylene blue, what else would you use?