Fish tail is slowly eaten away with black boarder

Hello, so one of my guppies seems to have what I assume is fin rot, he had it over a month ago as well but I put it down to the other guppy pecking at him. I returned that guppy to the store cause he was an a-hole. Long story short i have 3 guppies now, they don’t bully each other, tank is 60litres. And now the same guppy has finrot again, it appears to have this black boarder at ends of tail and and the tail is slowly getting shorter and shorter. Is it ammonia burns or fin rot? I’m treating the whole tank this time with Pimafix as of two days ago. Photos attached. Parameters are
Ammonia 0
Nitrite 0
Nitrate 5
pH 7

The only thing different I can see is pH is a lot lower usually it’s 7.4 but that could be the medication? Maybe nitrates are a bit lower too

 

Oh I forgot to mention I treated the fish in seperate tank the first time till he his tail looked healthy again. Then added him back to original tank

 

That is indeed bacterial fin rot. Pimafix can treat fin rot, but if it doesn't start improving then you'll likely need to switch to using a true antibiotic. Though that may be out of the question depending on where you live, I know fish antibiotics are banned in many countries.

 

That is indeed bacterial fin rot. Pimafix can treat fin rot, but if it doesn't start improving then you'll likely need to switch to using a true antibiotic. Though that may be out of the question depending on where you live, I know fish antibiotics are banned in many countries.

I have Melafix, will that be better? Should I use them together or separately? Yeah I doubt my local petstore will have it, as a lot of specialty stuff I have to buy online. I didn’t want to put him in another tank to treat cause it stresses him out, but should I be separating him from the other two?

 

I have Melafix, will that be better? Should I use them together or separately? Yeah I doubt my local petstore will have it, as a lot of specialty stuff I have to buy online. I didn’t want to put him in another tank to treat cause it stresses him out, but should I be separating him from the other two?

I think Melafix is supposed to be better for fin rot, but I believe you can use them together. Take my words with a grain of salt though, because I don't have experience using them, I'm just going off what I remember others saying.
As long as the others aren't bothering him you can leave him in, it's a mild treatment so they're fine to go through it too.

 

I think Melafix is supposed to be better for fin rot, but I believe you can use them together. Take my words with a grain of salt though, because I don't have experience using them, I'm just going off what I remember others saying.
As long as the others aren't bothering him you can leave him in, it's a mild treatment so they're fine to go through it too.

Ok sweet, thanks for the info, I will do a little water change and then put both Melafix and Pimafix in together, I have read a few other stuff about it being safe to put them other. Thanks for the quick reply as well