This koi is still young, and he was with other koi but I noticed he was acting sluggish so I took him out only to find that he may have been attacked by something. I'm worried if he'll be able to recover. His wound is terrible and I see fungus on his wound and is exposing his flesh in some places. I'm posting a picture. Any help is appreciated. I'm more worried about healing him than what caused it at this point.