Back in the concrete pond and after 8 weeks it's back
I also saw a reduction when kept in a green pond.
It seems that the origin of hikui is not really known, it could be brought by a virus, a liver failure or other metabolism problems.
The fact that puting the koļ in a mud pound has a good effect on the hikui is intersting because it could sugest that the better water quality of a mud pound (vitamins, oligoelements, monmorillonite..) help the metabolism problems.
Some treat the hikui by scaping the patches and cover them with a vitamin preparation or with propolis.
Marco