Cardinal Tetra - Bloating/obese, Buoyancy Problems, *purple Marks On Underside*

Pleased to report that, although the lead itself wasn't successful per se, they in turn put me in touch with a vet with fish expertise who was kindly able to help.  Currently, having completed the extended dose of eSHa 2000 to no avail, the cardinal tetra is in an "extended exposure" salt bath (sodium chloride added very gradually to the hospital tank following a water change), so she'll likely remain in that for a few days. Although potentially (additionally) attributable to the water change and diluted medication rather than the salt per se, initial signs today are that rather than resting belly-up interspersed with frenzied swimming on side/belly-up, she seems more "nose down resting" and swimming at a tilted angle and less-frenzied manner. Fingers tightly crossed.

For ref, here are 25-27 Mar's video clips in that order:
https:///youtu.be/p0uMOOfN7Vc
https:///youtu.be/VHL6tVAxUAU
https:///youtu.be/UBkuwTPWnrg [following water change and thereby dilution of medication plus salt (sodium chloride)]

[Edited to add: the one issue I forgot to mention is that the white mark on the caudal peduncle has re-appeared overnight - it seems to be right through it as opposed to superficial, so I'm keeping a very close eye on this.  I'm also glad that she was rather large to begin with and therefore had 'reserves' to see her through this week when she's not been able to eat.]

The buoyancy problem has been transformational and she's back to normal positioning at rest and swimming. https:///youtu.be/Y6nlwvjl-aQ
 However, the white spot that had appeared temporarily on her tail a fortnight ago, then re-appeared as a white mark last weekend, and was evident yesterday, is ravaging through her caudal peduncle and her tail looks like it mightn't be there in the morning as more than half of it has detached...

It is indeed - and that was this morning; it's now gaping. I could weep. I've spent the whole day trying to decide what to do in the absence of getting my hands on any Waterlife Myxazin, and wondering about whether to try a couple of alternative products with similar ingredients to it that I have to hand which are different from eSHa 2000. It's times like this that I really miss having an MA locally when I could pick up one of their products. However, I've just come full circle and added a drop of eSHa 2000 in to "tide over" the situation.

Thanks for asking about her. Resting in "correct", horizontal position (ie buoyancy resolved) but tail almost hanging by a thread when I last looked. Trying to keep my distance so that she doesn't move/respond too much, causing it to fall off (if it hasn't already).

Edited to add (29/03): the upper portion of the tail has fallen off and there's just a small join keeping most of the lower part on albeit it's drooping; fortunately, the ?muscle of the caudal peduncle that does the swishing movement is functioning well, so currently it's not adversely affecting her. Something very white is exposed - possibly cartilage/muscle, with the white ?spot on the outside. Buoyancy good. I'll keep monitoring.

Edited to add (31/03): the lower portion of the tail has fallen off plus the white ?spot and there's a slight fungus-like sprouting from the muscle, although not of too much concern just yet, as might just be re-growing tissues.

Edited to add (treatments):
Put in one drop of eSHa 2000 for 24 hours (28 eve > 29 eve), then water changed x2 (29 eve, 30 lunchtime), then the one-dose Interpet Disease Away carefully in two half-doses 30 eve and 31 morn. Contemplating whether a tiny bit of salt (sodium chloride) or one drop of eSHa 2000 might be required as the next step, and when...

Thanks - determined to my utmost for her as she's doing the same for herself and has fought so hard. She's stationed herself in the one place (mid-position in water column, buoyancy perfect - phew), where she's resting. She's aware of the odd grain of food dropping in but I don't think she's eating it, but equally she doesn't seem distressed in any way. She wiggles/responds to me if I approach, and thankfully enough of the caudal peduncle is there at the moment to enable that, although it's pitiful to see no tail at all. [NB. Photo looks as though she has no fins at all but I caught her in action, moving across the tank, which likely explains hidden fins. Confirmed that all other fins present and correct, including adipose fin - just about!]

Difficult to tell. Much the same.
Unless the situation is markedly worse tomorrow, I think I'll probably wait until the full dose of Interpet Disease Away has been in the tank for 48 hours (ie until tomorrow), then dilute the medication through water changes, to see if I can get her eating again. That will be a fortnight of no eating (and photos suggest she's considerably slimmer) which concerns me as she needs to be more robust generally and especially if I need to re-medicate. I also want to take some photos to see if I can compare with previous ones to ensure that no more of the caudal peduncle area has vanished.

Edited to update (02/04): Definite fungus sprouting out of the tail stump, not new fibres of re-growing tail as I'd hoped. Think the eSHa 2000 may have to be put back into use.
Edited to update (02/04, a little later): Bad news. Have just done a substantial water change and, by removing the decor in order to be able to siphon out the uneaten food debris, and with the sunlight shining in directly as it does for a short spell at this time, I managed to catch a good look at her. What I thought was fuzziness/fading of the red colour around her chest area yesterday, visible to my eyes but less so in photos, and a bit of a puffed-up chest visible to my eyes but which I attributed to just her former shape but not visible in the side-on photos which indicated she'd slimmed down, is in fact dropsy - her scales are pineconed when viewed from below looking up and at certain angles. This might also account for why she was a bit more jumpy/nervous. I'm currently running carbon through a second filter to get rid of any remnants of the Interpet Disease Away, and plan to re-dose eSHa 2000 later, but hopes for being able to save her are now fading vastly... 

Such a sad outcome, so sorry this didn't have a more positive ending. 

I am so sorry, fcmf 

Sorry to hear about this fcmf. I’ve commented previously about the poor genetics of cardinal tetra and wonder if this may have had an influence here. Either way as usual your superb care is unlikely to have contributed to the loss of your fish, quite the opposite in fact. A good life has been had.