Guppy’s tail fin?

Hi, guys.. I just saw this spot on my guppy and was wondering if I should be concerned.. I don’t recall seeing it before.. could it be tail rot?
Thanks!

 

It’s hard to tell without more info. What are your water parameters? Tank size? Any aggressive tank mates?

 

Because both pictures are blurred, it´s hard to tell what it might be.

 

It’s hard to tell without more info. What are your water parameters? Tank size? Any aggressive tank mates?

Water parameters are good.. tank is 20 gallon tall.. Nothing in the tank but guppies.. but.. when I bought the guppies(5 total) they were in a tank with big goldfish and some of the guppies tail fins have been nipped on.. I will try to get a better picture

 

Because both pictures are blurred, it´s hard to tell what it might be.

I will try to get a better pic.

 

I will try to get a better pic. I just turned the light on and she looks worst. I am thinking tail rot? I have her in a tank by herself with meds.. but I am not sure she will make it

 

Look like some form of bacterial infection has set in near her dorsal fin. Also, she seems to be bottom sitting in that picture which isn't a good sign. If there aren't any live plants then I would do aquarium salt and daily 25% + waterchanges. The fin either looks like a big chomp has been bit out, or its just naturally like that.

 

This looks clearly like an infection. Try what RomanNoodles96 has already mentioned.

 

Sadly she didn’t make it through the night. I want to thank all of you for your advise.