platy help me please!!!!!!!!!!

Question
Hi, my platy has gone all black on and around the back fin what does this mean?

Answer
Hello Kean:  Could mean many things.  It may be an aggressive issue in the tank and that will make some fish either pale or grow darker as a means to hide.  It could also just be genetics and the fish has turned from juvenile coloration into its adult coloring.  Most diseases are not dark so I doubt that it is a disease.  Does the fish act normal??? is it eating?  Is it hiding?  Also I will need for you to get your water tested and report back to me the chemistry values.  Let me know... dave