Su questo animale

I believe they are comet goldfish. I won one at a carnival and the other I bought from PetSmart. One goldfish’s fins are turning black, I thought it was the ammonia in the tank but his fins aren’t getting better. I got them because I was sad and didn’t want them to die, I am not in a good financial situation to give them the adequate care they deserve. Aquarium and everything I have comes with them too. see pictures for the items included!