I am having ongoing problems with my pond which have been going on now for around 6 weeks. Fish flashing on the bottom drain and pond sides and some red areas along the dorsal fin and in the tail fin. At first I had some Nitrites in my water so I did a water change and cut feeding. The flashing continued though and I found some fins dibilitating with rot. I have scrapped them all till I'm blue in the face multiple times and have only found what I thought was Chilodonella once. I treated with Acriflavin powder and salt and it seemed to perk them up but within a week or so the flashing started again. All feeding was stopped at the start of the treatment so when I tested my water everything was fine inc no Nitrites. When they had been flashing again I then treated by salting up to 0.9%, left for 7 days and then reduced to 0.6% for another 7 days(I did some scrapes again and again found nothing). I did leave the salt at 0.6% a little longer for 9 days but I then had a fish jump out of the pond yesterday and a Showa is looking quite dibilitated with mucus build up and fin rot in the tail fin I changed the water yesterday so it should now be salt free. They seem ok but I'm worried about major bacterial problems. Is there anyone knowledgable in the Hillsborough area of Sheffield willing to come and have a look and see what I'm doing wrong as I'm a bit at my wits end, it would be hugely appreciated I have some pics but the uploader wouldn't load them up. Thanks for any help and advice.
Thanks for your replies. If I'm honest I still believe it's parasites that I'm missing but god knows how for the amount of scrapes I've done. I received a number for Ritchie Bunting so I've contacted him and he was coming tonight but I've had to self isolate so hopefully he'll get over next week and find out what's happening. My air pumps are just underneath my decking where my filters are so any fumes getting into them would only be from them or any equipment in there. The only thing I could think of to do it would be the Heat source pump? but I would've thought I'd smell them myself. Thanks for all your help and I'll post an update when Ritchie has been.