Internal parasite?

Hello World, I have been fishing keeping for 15 years, not a novice, but new to forums ( is there a plural, 'foruming'?). I heard there is a wealth of knowledge on these sites, so can you help me identify a problem.
I have a black Emperor tetra with a white lesion protruding from his abdomen. I have successfully dealt with most common fish diseases over the years, but not to sure on this one.
My instincts tell me the fish has worms, I would like confirmation of this before I take my shrimps and snail out of the community and nuke the tank with Flubendazole.
Thanks
I'm Will

Tank size: 32x22x14 inch
pH: 7.2
ammonia: 0ppm
nitrite: 0ppm
nitrate: 20ppm
kH:
gH: Haven't tested these, but live in hard water area.
tank temp: 23.5 C

Fish Symptoms (include full description including lesion, color, location, fish behavior): White lesion protruding from abdomen, twitches while swimming, try's scratching up against plant leaves and rocks. Eating less.

Volume and Frequency of water changes: 25% once a week, if not more I enjoy doing these.

Chemical Additives or Media in your tank: TNC Carbon 4ml a day, TNC Lite 12 ml twice a week. Fluval 404 sponge mechanical filtration, Matrix and bio rings for biological filtration.

Tank inhabitants: 6 Panda Corys, 9 red Phantom Tetra, 4 Black Widow tetras, 3 Black Emperor tetras, 6 praecox rainbows, 2 cobalt gobys, 1 bolivian ram, 1 nerite snail, 4 amano shrimp.

Recent additions to your tank (living or decoration): Crinum calumistratum

Exposure to chemicals: Only what I dose for plants

Digital photo (include if possible):

That looks more bacterial to me.

Whereabouts in the world are you? I'd recommend esha 2000, if you can get it; it's shrimp safe as well, which is a bonus although the snail might need to come out, if you can catch it.

Hi Will and welcome to the forum

I like your choice of fishes, you have some of my favorites

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I doubt it is worms. Any chance of another picture from the front and front half looking back, or a video of it.

Thanks for the reply guys, since the post the white lesion has noticeably reduced in size, without any treatment, but has a bigger red ring around it.
Another reason I ruminated worms was because the fish has been passing white faeces.
I'll post more photos tomorrow.

@fluttermoth I have no experience with Esha 2000, would it be more effective than Melafix?

@Colin_T This selection of fish is one of the most enjoyable community tanks I have compiled, movement in all areas and levels of the tank and very compatible.

Thanks for your replys

A white sore with red around the edges (like a pimple) can be an ulcer starting to develop. If the white bit pops or disappears and leaves a red open wound then it is an ulcer and you will need some anti-biotics, preferably a food with anti-biotics in so the filters don't get killed off. Also the medicated food (with anti-biotics in) works a lot more effectively than treating the tank.

Stringy white poop can be worms or an intestinal infection caused by different types of bacteria (including Tuberculosis) or protozoans. However, with TB the fish usually swells up and becomes really fat overnight, they stop eating, do stringy white poop, sit up by the surface and breath heavily, and die within 24-48 hours of these symptoms occurring.
The emperor tetra doesn't show the other symptoms so I doubt it is TB.

With internal protozoan infections (spironucleus) the fish lose weight quickly and become skinny, and do stringy white poop. They usually die within a week of showing the stringy white poop.
The emperor doesn't look skinny so this is unlikely to be the cause.

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There is or was a medicated food used to treat goldfish ulcer disease, I would look for that and see if it helps. It should also help with the stringy white poop if that is caused by an intestinal infection. You feed the fish as much medicated food as they can eat, 3 times per day for a 1-2 weeks, or as directed on the packaging. If there is no improvement after a week then it isn't going to work and you will need to look at other options.

Metronidazole can help with intestinal protozoan infections, however, at this stage I would avoid that medication because the fish does not appear to be suffering from a protozoan infection.
*NB* Metronidazole should only be used as a last resort medication for fishes with a specific protozoan infection.

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I would increase the normal water changes and do a 50-75% water change and complete gravel clean each week rather than 25%. Big water changes dilute things more effectively than small water changes.

For this issue, I would wipe the inside of the glass to remove any biofilm, then do a 75% water change and complete gravel clean each day for a week. This will dilute any harmful pathogens that might be in the water that might be contributing to this issue. The big water changes will not harm your fish as long as any new water going into the tank is free of chlorine/ chloramine and has a similar water chemistry to the tank.

If there is no major improvement in the fish after 2 big water changes and gravel cleans, then start feeding medicated food. But do a couple of big water changes and gravel cleans first and see if it helps.

You should also clean the filter materials if they have been done in the last week.

Nearly everything in the entire known universe is more effective than Melafix, IMHO.

Melafix is just Teatree oil. It has its uses; mostly as first preventative, to stop any fungus forming on a wound, for instance, but once any infection or diseases has really taken hold, then its just not strong enough (again, IMHO).

White faeces can have a multitude of causes; I wouldn't worry about that at the moment.

Hello and thanks for your time, some great info. @Colin_T

The lesion has definitely got smaller, see updated photo. Will give the walls a wipe, gravel vac and do a large water change tomorrow.
The lesion appeared abruptly, I envisioned a worm rupturing the abdomen. Its been a while since I have seen an ulcer, this seems the likely villain now and hopefully quickly solved without meds.