Melafix is an all natural solution additive that is great for use during quarantine or following handling of your Koi. MelaFix is an all-natural medication derived from the leaves of the tea tree. In the transport of fish, no matter how careful we fishkeepers are, fish can become injured. This may occur during the interaction between fish while in transit. Any slight abrasion or to skin or fins provide an entry point for bacteria and fungus to invade your Koi. The effects of these bacterial infections can cause eroding fins, localized ulcers of the skin, and mouth "fungus". True fungus is a secondary invader and attacks damaged/dead tissue.