This is a discussion on fungus infection within the Tropical Fish Diseases forums, part of the Freshwater Fish and Aquariums category; -->
based on the description, i'm pretty sure my male swordtail has body fungus. what medications do people recommend for this issue?...
There are several anti-fungal meds available, but do some more research (especially looking at google pictures) of Columnaris. It's bacterial, but it often fools people into thinking that it is a fungus.
This is kind of expensive, like all API stuff:
Using the melafix probably won't hurt, but I don't think it will help with columnaris if that's what you have, since it's more of a gram-positive antibiotic. If it doesn't respond to the fungus meds or melafix, or it really starts to look like columnaris to you then treat with gram-negative antibiotic like maracyn-2 or furan-2. Read this: Columnaris (Flexibacteria); Aquarium/Pond Treatment, Prevention; Fungus, Saprolegnia