Help - Brand new goldfish - possible finrot? what do I do?

[FrostyGlassSlipper]

DH just bought a yellow goldfish today. It is to replace one we lost last week.

We already have 1 fancy goldfish in the tank.

The new fish is in a bag floating in our tank so that we can get the water temperatures the same. But I have notice he only has half a tail???? the top section is fine but the bottom section is completely missing and there is a redness inside the bit near the stubby end. This makes me think he may have had his tail eaten in the shop or have an infection or something.

So, what do I do? I dont want to add it to my tank if there is a risk it will infect/kill the existing fish we have. But if this is something fixable then I'm happy to look at that - I just dont want to leave this new fish in a plastic bag for too long as that doesnt seem very nice.

Take it back to the shop. Do you have a spare small tank in the meantime? Large tupperware box maybe? Fill it with water from the tank and leave the new fish in there.

If you can't get back to the shop, phone them. They might advise putting some potassium in the water or something to help it heal.

We've taken the sealed bag out of the tank and I'll put it into a friendlier box later.

DH wasnt too impressed with the shop to be honest and now he's very cross.

Now we feel bad and we're not sure if we want to send the new fish back to the horrible shop. We've put it in a bowl. After testing his original water it was high in NO2

So, what do I do? Shall I try and treat it? Is it treatable?

How long would I need to keep it apart from my old fish?

You can get water treatments for finrot - which I can testify do work after several attacks due to our (ex) sucking loach's attentions on his neighbours.
However I think it might depend on how far advanced this is - I seem to remember reading that once the infection gets into the main body of the fish it is often fatal.
Having said that I have rescued some from nearly-no-tailfin situations so it might be work a go.
Just be aware that if you have 'scale-less' fish in the tank too (clown-loach, corrys etc ) then you have to halve to dose, though as you are talking about a goldfish I guess it's unlikely that you will have those sort of companions, but thought I'd mention it.
It is also fatal to crabs - we had some fresh water crabs at one time, until a certain medication....ahem....incident.

Thanks for your help.