Very Sick Cory

• 10 Gallon tank, with filter and heater, temperature around 25-26 degress celcius.
• Stocking in the tank includes a betta fish and 5 corydoras catfish
• I do a 10-20% water change every week as this is a newly cycled tank. Water is treated with Prime Concentrated water Conditioner and substrate is vacuum every time there is a water change

Betta (Tiggy) was already in the tank for about 2 weeks before corydoras were added. At first, the betta didn't seem to like them very much but after about 2 days Tiggy started ignoring them for the most part.
However the smallest corydoras lost an eye in the initial introduction and then lost it's barbels about a day later. 2 of the other cory cats also damaged a little bit of their barbels in the following 2 weeks so I changed out the substrate to plant sand and all the other cory cats are happily swimming around the tank now with no new injuries but the smallest one has developed a white cotton rot around it's mouth. The white ring started around his injury site so I thought that it might have just been his injuries since he was still swimming with the other cory cats and didn't seem that bothered. Then I went away for the New Years and I came back to find his mouth rotted away and he is just hiding now away from the other corys.
I've ordered some medicine and have set up a quarantine tank but I was just wondering if I should just treat the whole original tank or should I move the sick cory?
Furthermore, should I remove the single corydoras or all of them if I were to use the quarantine tank?
I've attached a photo of the cory below but as you could imagine, he's a pretty small guy and it's hard to see.

 

Please euthanise it.

 

although it breaks my heart, if it's mouth has rotten away, I agree with DoubleDutch.

 

If you really think that I should then I will but is there really nothing we could do for it? How would euthanasia work on fish?

 

If you really think that I should then I will but is there really nothing we could do for it? How would euthanasia work on fish?

Only thing is to put it out of its missery.
Blast in the head or use of clove oil.
Sorry

 

Only thing is to put it out of its missery.
Blast in the head or use of clove oil.
Sorry

I understand. Thanks though.

 

say goodbye to him for me

I'm so sorry

I love cories, and all fish, it feels horrible..

 

I'm sorry for your loss.

Reading how many injuries there were I would have a better look at your stocking and water quality. If his mouth was 'rotting' away this might be a fungal infection and could potentially be contagious. It's hard to see on the picture though.

Good luck.

 

I'm sorry for your loss.

Reading how many injuries there were I would have a better look at your stocking and water quality. If his mouth was 'rotting' away this might be a fungal infection and could potentially be contagious. It's hard to see on the picture though.

Good luck.

I've bought some medicine and now that I understand the symptoms a bit better I'll keep an eye out in my main tank for white spots. I've also ordered a general medicine for rot that I will dose my tank with if any of the other fishes start getting white lips.
Thank you!

 

say goodbye to him for me

I'm so sorry

I love cories, and all fish, it feels horrible..

I feel absolutely horrible that it got so sick whilst I was away but we must all learn for our mistakes, I'm just sorry for the cory right now, I'm waiting for clove oil to arrive but in the mean time I've removed him from the main tank and have put him in quarantine just in case it is infectious.

 

Ow