What could this growth be - and best action?

Hi, Elsa is sick - I noticed he was lethargic and not himself about 2 weeks ago. Then he swelled up, and subsequently stringy poop - initially usual red colour, then grey-white.

He went into a hospital tank last Friday, with aquarium salt (1 tablespoon in 15 litres of water) and first dose of Interpret antibiotics. Small water change (c. 10%) and second dose of antibiotics on day 4 (Tuesday). Another 20% change today.

The swelling went down. Pine cone scales became apparent but have since gone flat again. Today there’s this thing that is less a growth and more looks like it’s ruptured from inside

What is it, and what is the best / kindest thing to do now? Thanks for all advice and experience.

water:
pH 7.2
KH 10
GH 7-14
Nitrate 10
Nitrite 0

no idea what you are referring to. post pictures from the side

Unfortunately not possible. I’ve circled on the attached photo to assist

If it were me, I would treat with another round of antibiotics and perhaps a bacterial med also...I like Furan-2. Continue salt and water changes. Look closely to be sure there’s nothing parasitic in or around the growth. With it having a stem to it, it may possibly burst and go away. If it’s a tumor, it shouldn’t be a malignant one the way it is growing. Keep us posted.

One more observation...does it look like it is coming out of his anus? If so, it is a prolapse which may explain the substance inside. Perhaps poop. In that case, I’m sorry to say it may be better to euthanize him. I use the clove oil method. Please let us know where it’s coming from.

Hi Deanasue, thank you so much for your advice and I’m sorry for the late reply. I only saw the first one for some reason and did as advised - and I can’t see anything parasitic- although any guidance on signs you would look out for are welcome.

update: there seems to be a really good response to a further dose of the antibiotic, more activity, eating (2-3 wafers fed individually twice a day), and coming to the surface when we open the lid wide or come to the floor and sit by the tank.

Then I just read the second message... It doesn’t look like it’s from the anus, it’s really more lateral and like it’s coming from the flank. (Which still doesn’t seem that promising if it was me I’d not be happy!)