Thanks, both. I've replayed it over and over in my mind and think I am to blame, though - normally, I "forewarn" everyone and calmly chat to them that I'm about to undertake their water change, whereas I was a bit distracted on Fri and a bit
too methodical and efficient - whisking out the hornwort and java fern, then realising I'd a couple of cuts on my fingers which were stinging from the water and grabbing a towel, then experimenting with the spray bar which ended up sending the water upwards towards the rear/back of the tank. If the fish had inadvertently accompanied the plants out of the tank, then lifting the neighbouring towel might have sent it skidding under the fishtank cabinet or it may have leapt out of the plants and under the fishtank cabinet while I was rinsing my cuts under the tap before putting on gloves. The fish transpired to be the one which enjoyed surfing the water current and swimming vertically in it along the opposite side of the tank - gutted to have lost the quirky one of that shoal
- so it's possible it may have availed of the several seconds' experimentation with the spray bar and ended up catapulting back the couple of inches straight through the slat.
As you say, though, and given how dry it was when discovered, this surfing fish which had taken to splashing at the water surface and in the hornwort may actually have escaped out pre- water change.
Separately, I have the harlequin with the intermittent lesion on its side currently under eSHa 2000 treatment in the hospital tank - it looks like a recurrent injury but may be a bacterial infection (no sign of parasites) albeit not as deep as the ulcer-like hole one of the female x-rays had. I may have mentioned before that his spine is twisted slightly in an S shape when viewed from above. Post- water change, he was shoaled up with the others rather than in his usual quiet spot near the top on his own, and I noticed how pale he was in comparison with them. I hadn't treated him before now but thought this was the opportunity to do so while he is constitutionally still strong and eating but does seem to be declining somewhat. The treatment may not help but I thought it worth a try before too late and to avoid any regrets.