Sick Fantail Goildfish?

Question

5 gallon tank with bamboo and some other plants. It is all orange. Over a couple of days he start growing a blak spot on his head. Then a light black line under his belly. And bleeding on his right side of his body. The bleeding looks internal. Now it has touble breathing

Answer 1

I'm guessing you're seeing ammonia poisoning, which is leading to black chemical burns, and the stress allowing the blood stream to become septic (the hemorrhaging inside).  Start by making sure the bamboo has a fair bit of its leaves and stalk above the water line, as if fully submerged, it will rot and die, leading to ammonia trouble.  Then, you will need to do more frequent water changes until you can get a 20 gallon tank for your soon-to-be 8" Goldfish.  After that, I would remove any activated carbon from the filter and start treating with Triple Sulfa, Maracyn 2, Trisulfa, Furan 2, Kanaplex, Maracyn TC, Metronidazole, Flagyl, Hexamit, or similar gram negative effective medications.

Answer 2

Its cuz you have him in such a small tank! He needs 20+ gallon tank to stop this groth stint he has that is making him internale organs keep growing and killing him. Bigger tank or dead fish, your choice.