What is having a goldfish really like?

A goldfish is a bit of a starter pet – they don’t need walking, don’t eat a lot or need a fancy diet, and the tanks don’t need heating. They are direct descendants of wild carp (Cyprinidae), and a simple, easy pet, you would think. Just add water and a pinch of fish food now and again.

But when you look further into them, there are some surprising facts that might make you take a moment before committing to that harmless-looking fish. Did you know they were first bred for food before becoming prized ornamental pets? (‘Goldfish and chips please. Easy on the salt’), and were first domesticated in China during the Jin Dynasty (265–420 AD) from dull, grey-green Prussian carp.

Are they really that boring?

I had a goldfish once, and I would say they don’t do much, and at the time, I didn’t know if you could teach them tricks. Mine just swam about and ate. And pooped. But I find that Goldfish are not inherently boring. They are supposedly highly intelligent, can recognise their owners’ faces, and have memories that last for months. They only seem boring if they are kept in a small, empty bowl or tank that lacks mental stimulation or tank mates. And yes, they can be taught tricks using positive reinforcement (pairing a visual signal with a food reward), you can train them to swim through hoops, follow a target, play mini soccer, even be trained to do the limbo! (I wonder how long that took).

The common-or-garden type goldfish are actually called ‘Common Goldfish’, and are similar to another one, their cousin the ‘Comet Goldfish’. Both have similar needs and only vary slightly in that ‘Comets’ are sleeker and are slightly smaller in build with dramatically flowing forked fins. ‘Comets’ have a stout body and short, rounded fins. Both grow up to over 30cm in length, and share the exact same cold-water care needs.

Ailments and illnesses

Actually, most goldfish ailments are connected to poor water quality.

You might think your goldfish is doing tricks by swimming upside down, but this is actually an ailment, a swim bladder disorder, caused by constipation or excessive consumption of air. Because goldfish are voracious eaters and swallow air while feeding at the water’s surface, they are very susceptible to gas and digestive issues. If a goldfish does pass gas, you might see a stream of bubbles, but this can sometimes be mistaken for air escaping from their gills or swim bladder.

They can get Fin Rot – a bacterial infection causing ragged, frayed, or disintegrating fins, which needs water changes and use of a broad-spectrum antibiotic or antimicrobial fish treatment. Or Ich – White Spot Disease, a parasite that shows as tiny white dots on the body and fins, that again needs specialised treatment.

My goldfish turned silver – I was quite proud that it didn’t die on my watch, but genetics were the reason - just as humans go grey with age, older goldfish often experience a natural loss of their orange and yellow pigments, turning white or silver.

Poor Water Quality

High levels of ammonia, nitrites, or nitrates can cause stress and fade a fish’s vibrant colours. If the colour loss is uneven or the fins look eroded, it may be a symptom of ammonia burns or a developing infection.

Water is the be-all and end-all for goldfish, serving as their environment, respiratory system, and importantly, waste disposal. Because goldfish produce high amounts of waste, pristine, well-oxygenated, and dechlorinated water is essential to prevent toxic ammonia build-up and fatal diseases, and 20-25% of their water should be changed weekly to remove nitrates and replenish essential minerals – and that is an art in itself, so you don’t damage them in the process.

So you can’t just plonk the humble goldfish you won at the fair into a tank and hope for the best, they need just as much care and attention as any other pet!