I have a 550-600 gallon koi pond in my backyard. 2 koi about 2 years old. One recently developed an infection, I believe, involving a fin that got snagged months ago. The wound appeared superficial but now 2 months later it has gotten a bit more red and he appears to be developing Dropsy. I monitor every day and the "fluffy" appearance has become prominent the last 3 days. What are some things I can do to help my little guy out?