I noticed yesterday that one goldfish had what appeared to be a blueish-green fungus around his eyes. I asked my son who has better eyesight than mine to pull the goldfish out and get a close look at him. My son thought it was normal looking, although the color is odd being blueish-green.
Then today I noticed the one koi in the system (blue barrel with 10 goldfish + one koi) appears to have a blueish-green cast over half of his body. An internet search brought me to this possibility: Saprolegnia.
I did a search on this forum and saw nothing; figured I would start a thread and ask if anyone else has dealt with this.