The thing is with this parasites they will be on the sturgeon too, so not being able to treat them and then putting them back in the pond will just re infect the Koi.
I understand about the salt, and I have never put any in my pond. Only clay. Its as un treated as I suppose it can be, the only things I have used is Pp, over 12 days ago, and some FMC surpress and fluke m, in the summer.
I have a blue bowl, I told Paul to try and catch them, and I am sure he will.
I will let you know later how he gets on as for me, I am off to work. I wish I could stay at home but one of us has to be doing something.