What is my goldfish doing? Behaviour, normal and not

A goldfish does a great many things that look alarming to someone who has not watched one closely before. It hangs at the surface, stands on its head, spits out gravel, mouths at its tankmates and follows its own droppings to the bottom. Almost all of it is normal. A few behaviours, though, are the earliest sign that something is wrong, often days before anything shows on the body.

This page is organised by what you can see, in the words people use for it, and each entry says whether it is usually normal, when it is not, and where the full answer lives on this site. If you have never looked closely at a healthy goldfish, what a healthy goldfish looks like is the baseline everything here is measured against.

Start with three questions

Before looking up a particular behaviour, three questions sort most cases into “normal” and “worth a closer look”.

1. Is it new? A fish that has always rested nose-down after meals, or has always hidden behind the same rock, is showing you its habits. The same behaviour appearing this week in a fish that never did it before is a change, and changes are what matter.
2. Is it one fish, or all of them? One fish behaving oddly points at that fish: an injury, an illness, a harasser. The whole tank behaving oddly at once points at the water, because the water is the only thing they all share.
3. Does it stop? A fish resting on the bottom that comes up the moment the light goes on or food goes in was resting. A fish that stays down, clamped and uninterested, was not.

The time of day matters too. Goldfish are active from dawn, rest in the dark, and often look paler at night, so a fish found motionless and faded at midnight is usually asleep, as the sitting on the bottom page explains.

The behaviours, at a glance

What you see	Usually	Worth a closer look when	Full answer
Hanging at the surface	Begging	Gill covers working hard, mouth gulping	Gasping at the surface
Can’t get down from the surface	Buoyancy	It lasts more than a day or two	Floating upside down
On the bottom at night, upright	Resting	It is daytime and the fish is clamped	Sitting on the bottom
Lying on its side	Not normal	Always	Sitting on the bottom
Swimming sideways, nose down, tail up	Buoyancy, often after meals	It persists or the fish stops eating	Floating upside down
Swimming in circles	A small tank, or a spawning chase	Spinning it cannot control	This page, below
Darting and scraping against decor	Irritation	Always	Flashing and rubbing
Wobbling in place without moving	Shimmying, which keepers read as stress	Always	Flashing and rubbing
Pacing up and down the glass	Begging, or a reflection	The tank is small or the water is poor	This page, below
Hiding	A new fish, or bright light	A fish that never hid before	This page, below
Chasing another fish	Spawning, in spring	The chased fish stops eating	Chasing and bullying
Spitting out gravel	Sifting	The mouth stays open	Mouth problems
Eating its own droppings	Sifting	Never, in itself	This page, below
Blowing bubbles, clicking at the surface	Taking air with food	A fancy that floats after meals	Sinking vs floating food
Yawning	Normal, now and then	It is constant and the fish flashes	Fast or laboured breathing
Fins folded against the body	Stress or illness	Always	Clamped fins
Jumping	A startle or a chase	Several fish trying to jump	First aid

The rest of this page goes through each group in more detail.

Where it is in the tank

At the surface

Three quite different things put a goldfish at the surface, and the gill covers tell them apart.

Begging is often the explanation. Goldfish learn within days that people at the front of the tank mean food, and they come up to meet anyone who walks past, mouthing at the surface as if they had not eaten for a week. They have, usually within the hour. The behaviour page explains why begging is foraging and habit rather than proof of hunger, and why it is an unreliable feeding signal. Walk away: a begging fish loses interest and swims down.

Gasping looks similar and means something else entirely. The fish stays at the surface whether you are there or not, gulping, with its gill covers moving fast. Either the water is short of oxygen or the gills cannot take it up, and the gasping page covers what to do today: more surface movement, a water test, and a water change if anything is out of range. When several fish do it at once, it is the water.

Floating is a fish that cannot get down, however hard it tries. That is a buoyancy problem, covered below.

On the bottom

A goldfish resting on the bottom at night, or when the room is dark and quiet, is sleeping, in the way fishes do: upright, fins relaxed, gills moving slowly, often a little paler than by day. It rouses when the light comes on.

A fish on the bottom in daylight that does not rouse, with its fins clamped and no interest in food, is not resting. And a fish lying on its side is never simply resting, because a resting goldfish stays upright. Both belong on the sitting on the bottom page, which also covers how to tell a sleeping fish from one that has died.

Hiding

New fish hide, often for days, while they learn the tank. Goldfish also hide from bright light, from a busy room and from a tankmate that is harassing them. None of that is illness.

What is worth noticing is a fish that never used to hide and now does, especially if it also hangs back at feeding. That combination is often the first sign of anything at all, before a mark appears. Watch a whole feed to see whether it is being pushed out, and look at it closely in good light.

Against the glass

Swimming up and down the front glass, nose against it, is called glass surfing, and it usually has an ordinary explanation: the fish is begging where it is fed, or reacting to its own reflection, which is strongest when the room is darker than the tank. Softening the lighting, or putting a background on the tank, often stops it.

Persistent glass surfing in a fish with nowhere much else to go is a different signal. A tank that is too small for the fish in it produces exactly this pacing, and so does poor water. The tank size guide covers the first, and a water test covers the second. A fish that surfs the glass for months also wears its snout, which the mouth problems page describes.

How it swims

Sideways, nose down, tail down, upside down

These are all versions of the same problem: the fish is struggling to hold its buoyancy. It floats up, tips nose-down or tail-up, lists to one side, or ends up on its back, and the harder it works to correct it the more tired it gets.

It is common in round-bodied fancies and has more than one cause. Keepers suspect the gut and what goes into it: a large meal, or air gulped at the surface, pressing on a swim bladder that is already squeezed by the body shape. Infection and the shape of the body or bladder also occur, and no study gives the proportions. Keepers report that a short fast and a switch to sinking, soaked or high-fibre food helps some fish, but there is no controlled evidence for it. The floating page covers the causes, and why “swim bladder disease” describes the symptom rather than naming a cause.

What changes the picture: buoyancy trouble in a single-tailed fish, where the body-shape explanation fits less well; a fish that also stops eating or looks swollen; and a whole tank of fish swimming oddly, which points at the water again.

In circles

Circling has several ordinary explanations and one serious one.

• Too little room. A fish in a bowl or a small tank often swims the same circuit endlessly, because there is nowhere else to go.
• Sight in one eye. A fish that has lost an eye often turns and scans more than it used to, which can look like circling. The damaged goldfish page covers living with it, and many fish settle well in a stable tank.
• A spawning chase, which goes round and round the tank in spring.

Spinning or corkscrewing that the fish cannot control is the serious one. It can come from severe buoyancy trouble, a toxin in the water or an illness affecting balance, and it needs a water test and an aquatic vet’s opinion the same day.

Hovering in place, and shimmying

A goldfish hovering in mid-water with its fins gently moving is resting, and fancies in particular spend a lot of the day doing it.

Shimmying is different: the fish stays roughly where it is and rocks or wavers from side to side, fins clamped, without swimming anywhere. Keepers read it as a sign of stress, often from the water or from irritated gills, so a water test is the first step, and the flashing and rubbing page covers it with the related behaviour of darting and scraping against decor.

Darting and jumping

A single dash across the tank is a startle: a shadow, a door, a hand. Repeated darting, especially ending in a scrape against the decor, is irritation.

Goldfish jump when they are startled, when they are chased in spring, and when the water is poor enough that they are trying to leave it. A fish that has jumped once will jump again, so the lid matters, and first aid covers what to do if one is found on the floor. Several fish trying to jump from the same tank is a water problem until proven otherwise.

What it does with its mouth

Sifting, spitting and digging

Goldfish are carp, and carp find food by taking in mouthfuls of whatever is on the bottom, sorting them in the throat and spitting out what is not food. A goldfish spitting out gravel, blowing sand about or uprooting a plant is doing exactly what its body is built for.

The one version that needs attention is a stone that goes in and does not come out: the mouth stays open, the fish works its jaw and cannot eat. The mouth problems page covers that, and the substrate guide covers the grain sizes that prevent it.

Eating its own droppings

This is the same sifting. Droppings go in with everything else and come straight back out. It does the fish no harm in a clean tank, and it is not a sign of hunger or of illness. A floor that is always covered in droppings is a reason to siphon more often, and droppings that are long, pale and stringy are worth a look for their own sake, which the constipation page covers.

Blowing bubbles, popping and clicking

Goldfish do not build bubble nests. A goldfish blowing bubbles has usually just taken in air at the surface, while feeding or begging, and is letting it out. The popping and clicking sounds many keepers hear are the same thing heard from above: the mouth breaking the surface as the fish takes food and air together.

In single-tails that is usually harmless. In round-bodied fancies, air taken in with food is a suspected contributor to buoyancy trouble, which is part of the case for feeding them sinking food; the sinking versus floating page explains why.

Persistent foam across the surface is not the fish at all. It usually means a build-up of dissolved organic waste, and the aeration guide covers what a surface film does to oxygen.

Yawning and gaping

An occasional wide yawn is normal, and goldfish seem to do it to clear the mouth and gills. Frequent gaping, especially with flashing or fast gill movement, is a sign of irritated gills, and the breathing page covers counting the gill rate to tell the difference.

Spitting out food

A goldfish that takes a pellet and spits it out is usually rejecting the food: too large, too hard, stale, or unfamiliar. Soaking it, a smaller size or a fresh tub usually solves it. A fish that tries to eat everything and keeps losing it has a different problem, in its mouth rather than its preferences.

“Kissing”

Goldfish mouth everything they meet, including the glass, the plants and each other, because the thin film of algae and bacteria on every surface is food to them. Two fish that look as if they are kissing are usually grazing the same patch, or one is picking at something on the other. In spring, a male nudging and mouthing at a female’s flank or vent is part of the spawning chase. None of it is affection, and none of it is a problem.

What it does to the others

Chasing

In spring, one or more males chasing a female relentlessly, nose to her vent, is spawning, and the males will be carrying small white breeding tubercles on the gill covers and the front of the pectoral fins. It looks like bullying and is not, although it is hard on the female; the breeding page covers looking after her.

Chasing outside the breeding season is usually about food or space, and occasionally a fish persistently harassing a weaker one. The chasing and bullying page sets out how to tell them apart and when to separate fish.

Following and grouping

Goldfish are social. They shoal loosely, follow one another round the tank, rest near each other at night and feed as a group. A fish that has stopped doing any of that, and keeps apart from the others, is showing a change worth watching.

Why behaviour changes first

The practical habit that follows is simple: know what your fish usually do. A keeper who has watched a normal feed, a normal evening and a normal morning will notice the day something is different, and the healthy goldfish page is a two-minute routine for building exactly that picture.

When a behaviour is new

If you have found a behaviour that is new, affects several fish, or appears on the “worth a closer look” side of the table:

1. Test the water. Ammonia, nitrite, nitrate, pH and temperature. The testing guide explains the numbers.
2. Look closely at the fish in good light: fins, skin, eyes, breathing and the body from above.
3. Change water if anything is out of range, with conditioned water at the same temperature.
4. Watch for a day or two and write down what you see. A behaviour that settles once the water is right was the water.