George, a standard goldfish, was admitted to Lort Smith Animal Hospital in North Melbourne last week to undergo surgery for a tumour that was "affecting his quality of life". 

Dr Tristan Rich, who performed the intricate surgery, said 10-year-old George was unable to swim and eat properly, and was starting to "really suffer".

"I gave then owner the option of trying to take [the tumour] off, or putting him to sleep," he said.

He said George's owner, a woman, was "quite attached" to the fish, and wanted to do everything she could for him. 

The surgery, which included putting the fish under general anaesthetic, took about 45 minutes, Dr Rich said.

"It's a very fiddly procedure, and you have to be very careful about blood loss," he explained.

The surgery cost about $200, which is the same amount a dog or cat owner would pay.

Dr Rich said anaesthetic cost the same, no matter the species.

"It can be a few hundred dollars, and mostly it's charged for the standard anaesthetic, also depending on the time it takes. The actual procedure is quick and straightforward," he said.

"[But] it's quite fiddly, as you can imagine with an 80-gram fish, and you've got to make sure you can control any blood loss. He can only lose about half a mil [millilitre]."

It took three water buckets to anaesthetise George, Dr Rich said.

One bucket contained water heavily laced with anaesthetic, in which George swam until he was put to sleep.

The second bucket contained enough anaesthetic to keep him asleep, which travelled through a tube connected to George's mouth, flushing over his gills. 

Dr Rich said that, after the surgery was complete, George was released into the third bucket, filled with oxygenised water, and was left to recover.

"George is now doing great; he spent a few days in the tank, and is now swimming happily in the pond," Dr Rich said.

Dr Rich said that, in his experience, operations on goldfish were uncommon, having performed similar surgery just 10 times during his career. 

He said people often became attached to pets, "from goldfish to budgie", and that veterinarians valued the bonds between humans and animals, and did not discriminate between the species when trying to save lives.

"Every day I'll do something different like this - operate on a little frog, or treat budgies, lizards, snakes and wildlife," Dr Rich said.

Despite their size, he said goldfish could live up to 30 years if looked after properly.

"If their water quality is up to scratch; if there's enough room for a growing fish - about a few litres per centimetre of fish - and if the fish is fed a good-quality commercial diet, they can live for a long time," Dr Rich said.