He likely has a bacterial infection along with secondary fungal. If you have alot of fish like this i reccomend Furan-2 along with Kanamycin antibiotic. But theres the problem with guppies, their so cheap, and get sick so easily, that your better off just euthanizing it and buying a new guppy. Keep some medicine on hand that deal with parasites, bacteria, and Fungus, if you plan on breeding or getting serious about guppies. I'd hate to have you rush out and blow 25 dollars on meds for one little guppy. Kanamycin is a great broad spectrum antibiotic and will cover most of your bacterial problems. Alot of us guppy people order from kensfish.com, he has cheap medicine and i reccomend trying his Antibacterial food with Oxytetracycline. If not look around for some kanamycin cheap and go to petsmart and get "fungus cure" which is Furan-2. Just for your convience in the future if your serious about fish you will need somethning to cover your bases. Use it digilently when you do get meds too. Im gonna make it simple and put three medicines you should be able to find and are broad spectrum, to control your 3 bases in the future. The furan-2 and kanamycin can and should be used together. Don't ever use any medicine with another unless its safe.
Bacteria- Kanamycin sulfate -antibiotic
Fungus- Methylene Blue
Parasites- Rid ich plus- Malachite/formalin
