I'm new to the forum. I hope you can help with an injury to one Koi.
As background, our pond is approximately 1000 gal. We are in the Washington, DC area so the pond is currently approx 50 degrees. We don't have a lot of experience - the pond and fish came with the house - we have learned to maintain it. We have two large Koi and several comets. The pond is healthy as are all, but one, of the Koi. That Koi was attacked by a raccoon two years ago. He had a scratch down is side and what looked like a bite mark on his back. We initially treated him and the water. He has done well. The scratches have healed. There is evidence of healing to the wound on his back, although it has been slow to heal. He has been active, eats well, etc. Since the temperature dropped, we have stopped feeding, but he does not appear any more lethargic than any of the other fish. He recently developed what looks like a blister on the area where of the bite wound. The blister is raised and red.
We're not sure how to treat it, especially given the cold weather. I would normally treat with Melafix, but given the cold and the doubt about its efficacy expressed here, have not done so. I would greatly appreciate any suggestions.
Thank you,
Karen