I have a goldfish with a large 'bubble/growth' on it's side. It has managed with it for many years, but for the last week it can no longer swim upright. I feel too bad to kill it, and every time I think it has died and open the top of the tank it swims away on it's side. It still managed to eat, through some manoevering of it's body and mouth.
Is there anything I can do?

Just a few questions,
How big is the tank you have now, how big is the goldfish, how many and what are the other occupants? And what are you doing now to treat the tank, which products are you using?

Goldfish are prone to tumors and such, normally there isn't much you can do, unless you know how to properly amputate them ;) There are many causes of the tumors, such as malnutrition and maintenance of the tank. Goldfish are one of the dirtiest of fish, and the tanks needs to be cleaned on a regular basis.

Hi - thank you for your response! The tank is about 1m x 1/2m wide and has 3 goldfish in. I took them over from a friend of my daughter who did not look after them properly. The original tank was disgustingly dirty and was so small that the poor fish could hardly swim in the space allowed. This fish already had the growth when I inherited it (about 2 years ago). I suspect then based on your comment that the reason it got the tumor must have been due to the initial tank conditions
Is it a complex process to amputate the tumor? I can't bear the thought of killing it :(

I have never done the procedure myself, so I couldn't tell you how to go about doing it. We do have a great fish guy, he should be here either later tonight or tomorrow. He might have some better suggestions for you. Have you tried using a product called Melafix or Pimafix? They are an all natural product, I use them in my main tank care. It may not cure it, but if there is any bacterial or fungal infection it will help clear it up.

Hi, will check at our local pet shop, but it would be really great if you could ask your fish guy for some advice on the procedure. Thank you for your trouble