Originally Posted by Jade_the_frog
Thank you for your replies. Unfortunately we are not able to quarantine the fish as we do not have a another tank. Looking at it again today I feel the lump may be bigger so am thinking we may need to get him out. I’ve attached a photo. Do you think it could Neon Tetra disease?
It could be. Your original photo didnt suggest that, but that one looks more like neon tetra disease. Whatever, i think its not good.
If you cant isolate the fish you risk whatever it is spreading. I certainly wouldnt want to keep that fish with others. What about a 10 to 20 litre tote box? Small heater, maybe an airstone? Regular water changes?
As for treatment as you are UK, we cant get hold of the antibiotic treatments you might see suggested on sites like this unless you go to a vet. And its not worth going to a vet for a £1 neon tetra im afraid.
If you cant quarantine i wouldnt medicate the main tank, so i would up the water changes to daily to ensure the water is as pristine as possible and hope clean water can pull it through.
If you find you can quarantine then aquarium salt might help. As for medications, Esha2000 or Waterlife myxazin would be where i would start.
The other solution would be euthanasia as Joe suggests. My experience, small fish like tetras dont often pull through when issues become as pronounced as you are seeing, especially when you are as limited as we are on available medication.