Goldfish not eating

Goldfish are enthusiastic eaters that learn who feeds them and beg from anyone who pauses near the tank, so one that lets food drift past is hard to miss. Appetite is a sensitive signal rather than a dangerous one: it drops at the first hint of trouble, and a healthy adult can miss meals for a few days without harm, which gives you time to find out why.

A pause or a problem?

Two questions sort most cases: is it one fish or all of them, and is the fish otherwise normal? All the fish going off their food at once points to something shared, nearly always the water or the temperature. One fish refusing while the rest feed points to something individual: stress, constipation, an old fish slowing down, or an illness beginning. A fish that swims with its fins open and is curious about the room can be given a few days; one that is also clamped, floating, bloated or breathing hard cannot.

Will not eat, or cannot eat?

The distinction that changes what you do next, and it is easy to miss because both look like a fish ignoring its food.

A fish that will not eat shows no interest. Food goes past and it does not follow. That is the appetite question this page is mostly about.

A fish that cannot eat is the more urgent one. It comes forward, it clearly wants the food, and then something goes wrong: it takes a pellet and drops it, works its jaw repeatedly, turns away and comes back, or seems unable to close its mouth. What to look for, with a torch through the glass:

• Something lodged in the mouth. A piece of gravel picked up while grazing and not spat out is the classic case, and it happens often enough to check for first. The fish looks as though it has simply lost interest, and it is starving with food in front of it.
• Injury to the jaw or lips. From a net, from the glass during a fright, or from a spawning chase against hard decor.
• A growth in or around the mouth, which develops slowly — lumps and growths covers that.

Do not pull at it with tweezers or use any force. A goldfish’s mouth is easily damaged, and a vet can do it quickly and safely; the mouth problems page sets out what to do first, and the one careful method for when no vet can be reached. Finding an aquatic vet covers locating one, and this is a good example of a problem that sounds dramatic and is a short, cheap appointment.

The substrate guide covers the size question that prevents the gravel version: goldfish graze constantly, and the sizes that cause trouble are the ones just large enough to pick up and just large enough to stick.

Not eating, or not getting any?

Also worth separating, and the answer is in the watching rather than the tests.

Watch a whole feeding from across the room. A fish that comes forward, competes and is beaten to every mouthful is hungry and losing rather than off its food, and the fix has nothing to do with health. The pattern is common:

• Fancies against single-tails. Commons and comets are faster and reach food first every time, which is one of the reasons the two types are kept separately — how many goldfish covers the rest.
• Poorly sighted breeds against everyone. Telescopes, moors and celestials find food slowly, and cloudy eyes covers what else affects that.
• One feeding spot. Everything arriving in one place concentrates the competition.

The fixes are simple: feed in two places at opposite ends, use sinking food so it does not disappear at the surface, and allow enough time — the fish that eats last still needs to eat. The feeding guide covers portion and routine.

Telling the causes apart

Water comes first, as a common cause and the quickest to rule out. Ammonia and nitrite kill appetite before they produce anything you can see, and a tank that has drifted to high nitrate over months of skipped changes produces dull, disinterested fish. Fix the water and the appetite usually returns within a day or two.

Temperature is next, since goldfish eat in proportion to how warm they are. A pond in autumn or a tank in an unheated room cools the fish until it wants very little, and below about 10 °C (50 °F) a pond goldfish should not be fed at all; the temperature guide sets out the ranges and the pond guide covers winter.

Stress explains most single-fish cases: a new arrival, a move, a rescape, a boisterous tankmate or a tank next to a television will put a fish off its food for a few days. Constipation explains many of the rest, particularly in round-bodied fancies, and usually comes with a fuller belly, odd faeces and a tendency to float or sit; see the swollen abdomen page.

Suspect the food, too — feeding a sick goldfish covers how to restart an appetite and what a fish that spits food out is usually telling you. Flakes and pellets lose their smell and vitamins within months of opening, and a fish that mouths food and spits it out is often reviewing the menu rather than ill. A fresh tub, a smaller pellet or a frozen food settles the question.

What to do first

Test the water, correct anything you find with a temperature-matched partial water change, and check the thermometer. Then stop feeding for two or three days, which stops uneaten food spoiling the water. When you restart, offer a small amount of something different, such as a piece of skinned pea, a soaked pellet or a frozen food, once a day, and remove whatever is not eaten within a couple of minutes. Return to the routine in our guide to how often to feed goldfish once the fish is eating.

Watching for weight loss

The measurement that tells you whether a pause has become a problem, and the one most people take from the wrong angle.

Look from directly above. Seen from overhead, a healthy goldfish has an even, rounded width behind the gill covers. A fish losing condition narrows sharply there, and in time the back develops a slight ridge — the “knife edge” that keepers describe. From the front glass, a fish can lose a great deal of condition before anything looks different, which is why weight loss is usually noticed late.

Photograph it from above, against the same background, every week or two. A change that is invisible day to day is obvious across a fortnight.

And compare against the others. A fish of similar age and breed in the same tank is the best reference there is.

Weight loss with a good appetite is a different and more concerning picture — a fish eating normally and still thinning suggests something internal, often gut parasites, and it is a reason to see a vet rather than to feed more. A goldfish losing weight sorts that picture from a fish that is simply losing out at feeding time.

A ladder, not a panic

Because the answer to “should I worry?” depends almost entirely on how long it has been and what else is true.

When	What to do
Day 1	Nothing. Test the water. A missed meal is not information yet.
Days 2–3	Stop offering food that is not being eaten. Check temperature. Watch a full feeding to see whether it is competition.
Days 4–7	Try a different food — something frozen, a vegetable, a fresh tub. Look at the mouth. Look from above for condition.
Day 7+	In clean, warm water with no other signs, this is the point to ask a vet rather than keep waiting.
Any day	Refusing food with clamped fins, bloating, raised scales, gasping or floating moves it up the ladder immediately.

A very useful thing in that table is the last row. Loss of appetite alone is a weak signal; loss of appetite alongside anything else is a strong one.

Restarting an appetite

Once the water is right and nothing else is wrong, a few things genuinely help a reluctant fish start again.

• Fresh food. Flakes and pellets lose their smell and much of their vitamin content within a few months of opening, and smell is how a goldfish decides something is food. A new tub resolves a surprising number of cases — reading a fish food label covers what to buy and how much of it.
• Something strongly scented. Frozen bloodworm or daphnia are far more attractive to a disinterested fish than dry food, and gel food sits between the two.
• Garlic. Widely used in fishkeeping as an appetite stimulant, usually as a commercial preparation or by soaking food in garlic juice. The evidence that it restores appetite is thin: experimental work on garlic in fish, goldfish included, reports growth and disease resistance rather than appetite, and nothing shows that soaking food in garlic juice is harmless. Some keepers find it works, so it is a reasonable thing to try in small amounts, but not a substitute for finding the cause.
• A few degrees warmer, if the water is genuinely cold for the fish — raised slowly, a degree a day, and not above the normal range.
• Quiet, and the right moment. A fish that is unsettled will not eat with faces at the glass. Feed when the room is calm.
• Food where the fish is. A fish resting on the bottom will not chase floating pellets. Sinking food, placed near it, removes the problem.

Feeding a sick goldfish covers this in more depth, including what to do for a fish that is recovering or under treatment.

The pond year

Seasonal, predictable, and the source of a great deal of unnecessary worry.

Autumn. Appetite tapers as the water cools, and so should the feeding. From about 15 C downward, move to a smaller amount of an easily digested wheat-germ-type food, offered only if the fish come up for it.

Winter. Below roughly 10 C, stop entirely. The fish are barely digesting, and food that sits undigested in the gut does real harm. Fish that spend months on the bottom eating nothing are behaving correctly — sitting on the bottom covers the dormancy side, and a pond through the year covers the whole cycle.

Spring. The restart is the part that goes wrong. Feed too early or too heavily and you load a gut that is not working yet, into water whose filter is also still cold. Go slowly, follow the water temperature rather than the calendar, and expect the fish to be run down for a few weeks — feeding through the seasons has the bands.

When it is something else

A fish that has refused all food for more than a week in clean, warm water, especially one that is losing weight or passing white stringy faeces, has moved beyond stress and constipation. Gut parasites and internal bacterial infections both cause this picture and need different treatments; a vet with a faecal sample under a microscope can tell them apart. Very old goldfish eat less as a matter of course and may need soft, sinking food placed where they rest; that is age, not disease.

Preventing it

Fish in stable, clean water at a steady temperature rarely lose their appetite for long. Test regularly, change water weekly, keep the tank away from drafts and radiators, and quarantine new fish. Buy pellets in tubs small enough to finish within a couple of months, feed a varied diet, and feed only what disappears in a minute or two. A goldfish that is hungry at every meal is one whose keeper will notice the first meal it skips.