Urgent help please

https://www.facebook.com/photo.php?fbid=891071630921969&set=a.280483918647413.84212.100000574217640&type=1

Hope you can see that. This morn I came in to see this fish upside down at the front bottom of the tank. Her vent area is very red and rough looking. One side of her abdomen has lost its sheen and looks red and ragged. I took her out, put her in a small tank with an airline and added some Protozin as a short term measure because I have absolutely no idea what this is. It looks as if she is rotting from the vent upwards.

Can anyone help? I dont know if she is too far gone to treat. I have some Metronidazole if that will help, plus all the usual liquid type treatments.   

https://i.servimg.com/u/f39/18/91/93/25/bad_fi11.jpg

Not the clearest photo, but it looks like a bacterial infection, TBH I suspect it's too far gone to save, but in order of preference, I'd treat with Esha2000, myxazin, or melafix.
Good luck

I think this fish needs euthanasing.

I was just about to get the clove oil out, but she has passed away. Do I need to do anything to the tank she was in, as her partner is still in there, no symptoms so far. He is my favourite male and I am very anxious for him. I have done a water change and cleaned the bottom of the tank. How long should he stay on his own?

Assuming that you've had these fish for a while, i.e. weeks or months rather than days, and that they've not been in contact with any newly introduced (angel)fish in the last few weeks. Also assuming that the damage appeared overnight, and the fish was feeding & behaving normally yesterday. My best guess is that she's been the victim of a violent attack overnight (or possibly that she's been spooked by something during the night & then injured herself on some of the tank decor), either way, it appears that the damage has then become infected.

I've lost a few in similar circumstances, several years ago I had what I thought was a perfect pair, on their own in a breeding tank, they'd been together for several weeks with no sign of conflict, one night they were fine & happy together, the next morning she looked like she'd been in a food blender. I can only assume that the male turned on her in the night.

Do you have a bristlenose or other plec in the same tank?
More recently I had several fish developing similar looking damage overnight in a display tank. At first I was concerned that I had a serious disease or water quality issue, but to cut a long story short, it turned out I had a rogue male bristlenose (possibly trying to protect his eggs/young) once I removed him, the problems stopped.

Either way, I suspect treatment is unnecessary, but I would keep the male in isolation for at least a fortnight, and if you want to treat with anything as a precaution, I'd be using Esha 2000.

It is funny you should say that.  I have had the male for going on 3 years, he is getting old now.   No other fish in the tank but this pair.   The female, I bought at the beginning of January, I bought two, I grew them on a bit, and one of them was put with the male in March.  So they have been together about 5 months.  The male appears gentle and docile, but this is his second partner.  

His first partner died a year ago.  She suddenly appeared to have red marks around her head and went down rapidly.  Within a day.  At the time I thought it was an infection or even hole in the head.    I think there was a small woodcat and some corys in the tank also.  I am now wondering if the male is a Jekyll and Hyde.  She hasnt been interested in breeding for the last couple of months.  I really wanted to breed from the male, he is the albino pearlscale in my avatar.  I have some of his offspring which came from a coupling with a gold,  and they are smokey.  I suppose the nearest I might get is breeding from his offspring who will have his recessive genes.  

I feel a bit depressed about the whole thing tbh.

Sorry for your loss.
That's the thing with angelfish, there are highs & lows, and invariably the fish you really want to breed from is always an infertile, egg eating, wife beating, sociopath.
you can also guarantee that out of any spawn there will be one fish that is the best of the batch, the one fish out of hundreds that you want more than anything to keep & breed from, you can guarantee that if all it's siblings live, that fish will die mysteriously at about 5 months old.
Despite this, with care, patience & perseverance, with each generation you will find that the fish you're breeding are better than than those that went before.