dieases

Question
my guppies are Turing black. Can U tell me what this means?

Answer
It is hard for me to guess with such little information, however with the information provided, the best GUESS I have is a fungus which needs to be treated with a fungal treatment. If you can give me some more information, such as are they eating, swimming ok, breathing normally, and are there any other symptoms I could make a better guess. Let me know if you need more help or if you have any more information.