Not much of a reprieve.
One harlequin - the one which has been bobbing back and forth lately as its buoyancy has gone rather awry, with its tail lower than its body rather than the fish being completely horizontal - had an inflamed base of its right pectoral fin this morning. By mid-afternoon, I noticed the base of the pelvic fins were also inflamed. By early evening, the mouth was also affected. See video, with apologies for debris floating past as the tank was still settling from the water change: https:#//youtu.be/P_FKm2jCVzI [remove the # to view].
I decided to do a larger-than-usual water change on the tank in an effort to mitigate this, during which I viewed all the fish from above. Currently, I have 3 fish which concern me:
* the fish in the video above
* the x-ray tetra with the pop-eye which didn't respond to treatment but is doing fine in every other way
* a harley with a very curved spine when viewed from above albeit it looks absolutely fine when viewed from the front of the tank - its spine is in a slight S shape when viewed from above, with one side of the body twisted one way and the other side twisted the other way, and this is the fish which had the injury on its side and which disappeared lately but a fleck had re-appeared in the past day or so.
I don't plan to treat the last two in the list above but am contemplating whether to treat the harley with eSHa 2000 or whether to hope the water change might be sufficient. Views welcome; thanks.
I know the harlies and x-rays are getting older but I do wonder if there's something else going on in my tank which can't be measured by standard, home-based testing kits...