.  After this a younger koi also got signs of wounds in the tail region, and the fish was covered with a grayish layer (not fungus, more like a tone to the skin). So I figured MG & Formalin wouldn't help it much either, so I gave a 0 % salt dip. It seemed to do the trick. And it also got a dip with the rest of the bunch about a week later, and another one 0 days later (0%). This fish is doing better I guess. Wound seems to be healing. (But the sumi is almost gone (it's 0-0 years), and the sumi on my 0 yo Showas is also faded alot! I guess it's due to the high water temperatures I've had the last week. But the odd thing was that the sumi almost went out like a light bulb on the young koi after the last salt dip. )