We have a long established healthy pond. We've had two years of baby goldfish being born. One of the younger fish was being chased a few days ago by some of the others. It was born black and is still gradually changing colour so has black with flashed of gold.
We've just found this same fish sat on the bottom of the pond with green algae round its two sides. We thought it was dead, but with a gentle poke behind its tail, we saw the gills moving and it moved slightly to the side of the pond.
I'm not hopeful for it, but what's the best plan? Leave it to die where it is? Could it infect the others as there are twelve healthy fish in it? I no longer have a indoor tank or pump, so all I could do would be to put it into isolation in a large plastic box that I've used before now for isolation when I had some fish in an indoor tank.
Would I be correct in thinking I see the scales 'pineconed' i.e. slightly 'spiked'/sitting out from the body? If so, then it's very possibly dropsy, which itself could be because of a bacterial infection.
Your best bet, from what you describe, and also to avoid it being potentially picked upon, is to isolate it in the large plastic box. Daily water changes (with dechlorinator if using tapwater) ought to help in lieu of a filter which would ordinarily process the fish waste/ammonia. It might also be worth trying eSHa 2000 or Waterlife Myxazin to treat for bacterial infection.
Thank you for your reply. Sadly we were too late to rescue him/her. It disappeared into the depths of the pond; we kept looking and when it reappeared, it had already died, so we simply removed the body.
I'm hoping that perhaps the cause was damage by the chasing of the other fish which was more extreme than I've ever seen before and then an infection set in. We may never know but we'll keep an eye on the others anyway.