BIG Goldfish Ulcer [HELP]

My fish (been alive for 7+ years) is dying of what looks like an ulcer or some kind of infection.

Anyone know what this may be?

Goldfish Ulcer Disease, needs some form of anti-bacterial treatment, usually medicated food containing anti-biotics and or anti-biotics injected into the fish or added to the tank.

Vets are expensive so medicated food or see if you can get anti-biotics from the pet shop. Probably not possible in Canada due to restrictions on their use.

You can try salt but I think it's gone way past that point. If you want to try salt, add 2-4 heaped tablespoons per 20 litres of water and keep it there for 2-4 weeks. Change most of the water each day and add new salt water to the tank.

Waterlife Myxazin might be available or another brand of broad spectrum medication that treats bacterial and fungal infections. They might help but might not.