Simply Koi and More Koi

Hi
One of my koi has not taken any food for a couple of days and hovers around the filter return although it does follow the others when they are eating.
I caught it yesterday and noticed small stone in net which I think it spat out and it is constantly opening and closing mouth.
I had it out of the pond today again and sedated it to try and have a look, I have taken some photos but am struggling to attach them.
It has a small hard lump on bottom and back of throat which looks clean and is not inflamed and red.
The gills are nice and pink but there is some black residue around edges which looks like sedement from bottom of pond, I fed them some maggots last week and wonder if this koi has not been able to clear itself of sedement after feeding on bottom, is this possible.
The koi recovered ok after I had sedated it os its gills seem to be working .

Peter, usually when a fish hovers in the return flow it’s a sign of parasites, its what’s known as ram ventilation, have you checked with a microscope? Do a scrape and microscopic inspection for parasites

The gill should in fact be deep ruby red and not pink, pink and lighter shades usually indicates varying degrees of anaemia

duncan

Thank you for your reply Duncan, I haven't done a scrape myself yet so I asked local dealer who came round this evening and did one, the fish has seemed to be looking better and taking odd pellets but as the dealer had come round he did a scrape but found nothing on the fish.
He did a water test and found a trace of ammonia with a hanna test instrument although I didn't see any on a new NT labs kit but no nitrite was found.
I have put it down to feeding a higher protein food recently and now I have decided to feed wheat germ and only occasionally feed the higher protein food.
Thanks again for your input.
Pete