I've been having the same problem with my lionhead. first, a small black patch appeared on the top of his body, then it started to spread all over it. also, the tip of the fins: tail, pectoral, ventral... i've also heard black spots would appear on goldfish as a healing process, but because it's taking over his body i've decided to do more research and found out that it could be a disease called "myxobacteriosis" and the only medication for it would be "phenocide" by aquatronics. it turned out that aquatronics has gone out of business or have not been supplying the fish stores anymore and i cant find this medication. i've talked to the owner of my LFS and he found out that "kanacyn" could also be used for this disease. anyways, i'm not sure what's going on, but i did start a treatment with kanacyn today.
it says that "myxobacteriosis is due to either poor filtration, or overfeeding.
i'll let ou know what happens.
http://www.aquatronicsonline.com/hobbyist/hobbyist3.htm
here's a pic of him, but now it's even worse
