This is my first post on this cite, although I wish it was under better circumstances! I recently bought a silver metallic Fantail goldfish from PetSmart last Thursday night (3 days ago). I've never had any problems or issues in the past with them. I was told by the associate that they just got these Fantails the night before I bought Barbossa (goldfish in question) so I'm assuming that because Barbossa is around an inch long that he's around 1 month old. When I got him home, I placed him in my 75 gallon tank with several plants, 5 mystery snails, 7 amano shrimp and my Black Moor that I've had since the beginning of January. I questioned his overall health once I saw that he seemed to put forth more effort to swim than what my black moor showed, but I brushed it off and figured that my Emperor 400 filter must have a stronger current than what he's used to. During that first night, I also noticed his fins where jagged and not as "pretty" as my black moor's fins, but I brushed this off as potential bullying by other fish or lack of nutrients from competition for food and I thought he would improve once he's been in good water for a couple days and had time to heal. However, by Sunday (day 3 since I got him) I noticed that he showed no improvement. Barbossa's dorsal fin currently looks slightly jagged, and frayed with a slight white coloring closer to the tips, his back right bottom tail fin also shows some slight white closer to the tips with jagging along the tips, there has been no visible change since I got him. He also prefers to swim with his dorsal fin against his body rather than upright like my black moor. I am not sure if this is another symptom, but his coloring in his fins may be off, there's dark grey veins with the remaining fin being a clear color. However since I've only seen him in this condition, I am not sure if that's natural or not for him. Barbossa eats well, and swims throughout the tank with occasional dashing and even playing with my black moor. He doesn't show any red coloring in his fins or on his body, nor have I seen him rub against anything in my tank. I think that most likely the poor water conditions/overall poor living conditions that he's been living with at the fishery his whole life is the cause of his potential fin rot. My tank's water perimeters are all at good levels Ammonia at 0 ppm, Nitrite at 0 ppm, nitrate is 10 ppm, Ph is 7.2. I have been told that a salt treatment for a week in a hospital tank may help him, however I do not know the right formula. His hospital tank is roughly 10 gallons with a whisper filter and an air stone, filled with new water. In conclusion my main concerns are 1) have I caught it early enough to treat him without him having any long term effects and 2) Since I had him with my healthy black moor for a couple days, what's the chances that he will also contract fin rot?