Yes I know how little it was I was just going to increase very slowly as Jumbo was in such a weak state ... he was probably going belly up because of being too weak to escape the current and amount of aeration in the QT tank .... not surprisingly he didn't make it as he was in such a bad way.
Anyway with the panic over had more time to scrape all the fish and after closely checking over all mucus samples (taken from along the operculum edge, belly to cloaca and sides) I found no further parasites .... except for one fish which had something very small moving (even at 800x couldn't get a positive ID on it) but I have a feeling it could have been two very small/young Costia by the movement.
It's interesting what you say about Costia always being present ... I have heard before that some believe that Costia and other parasites are always present in a fishes cloaca but on a lot of forums people debate about how Costia has got to their pond e.g. slugs falling in or bird droppings etc, etc. and talk of their pond being "clear" of Costia after successful treatment.
Do you think that no further treatment of the pond is required then at the moment .... even if one of the fish might (although not confirmed as mentioned above) still have a couple on it?
On most forums it seems that finding even one Costia in a barrage of scrapes is dealt with immediate heavy duty whole pond treatment.
Also although it may not be related can I also ask your opinion of whether "Lunking" (quickly breaching the surface then diving and blowing air out gills) is a good/bad indication of anything?
... a few of my fish started doing this regularly for the first time this year even when in apparent perfect health with optimum water chemistry. My water is only 4.5 feet deep so not a deep pond and the only difference is this year it has an airlift return that uses very fine bubbles so will be increasing o2 saturation. It's something I've been watching for a while now and trying to gather info on as there doesn't seem to be a definitive explanation for why fish do it and the opinions I've had are diverse from it being "an indication of parasite infestation" to "they do it for fun" ....
![Smile :)](./images/smilies/icon_smile.gif)
..... I'd be interested in what you think with all the experience you've had.
Thanks for your time Duncan ...
*later addition* ..... just been to pond and one of the koi that tested clear yesterday on scrapes is flashing madly at the walls and drain .... so I'm off to scrape again ...
![Sad :(](./images/smilies/icon_sad.gif)