Rehoming a goldfish you cannot keep

Several pages on this site arrive at “rehome it” and stop there. The stocking guide says it about a tank with too many fish, the chasing page says it about a fancy living with a comet, and breeding goldfish says it about a spawn nobody planned for.

This is the page that says how — and, more importantly, the page that says where not to.

First: does it actually need rehoming?

Worth a few minutes, because a good share of the fish people set out to rehome do not need to go anywhere.

If the tank is overstocked, the options are fewer fish or more water, and more water is often cheaper than expected. A food-grade tub or stock tank holds several hundred litres for a fraction of what glass costs — the tank buying guide makes that case, and how many goldfish you can keep sets the numbers you are trying to meet.

If two fish are mismatched, check whether it is really the fish. A fancy outcompeted by a single-tail can often be fixed by feeding at two ends of the tank and switching to sinking food. Where the mismatch is structural, rehoming one is the right answer — goldfish tankmates covers which combinations never settle — but it is worth being sure.

If a fish seems ill or is behaving oddly, test the water before deciding anything, and run it against signs of a healthy goldfish before concluding it is unplaceable. Most behavioural problems in a goldfish tank are environmental problems wearing a disguise.

If you are moving house, you probably do not need to. Goldfish travel better than people expect, and handling, netting and moving a goldfish covers doing it over a long distance.

If your circumstances have genuinely changed — time, health, money, allergies, a household change, a bereavement — then rehoming is the responsible choice and the rest of this page is for you. There is no shame attached to it. A fish that goes to a keeper with space and time is better off than one kept out of guilt.

Where goldfish actually go

Ranked by how the fish tends to do, rather than by convenience.

Route	How it usually goes	The catch
Someone you know with a set-up tank or pond	Best outcome available	Rare to have one to hand
A local aquarist society or goldfish club	Excellent, and badly underused	You have to find and contact one
A pond owner	Very good for single-tails	Not suitable for fancies
An independent aquatic shop	Often workable	Call first; expect credit or nothing
A fish rescue or rehoming group	Real, and variable in quality	Regional, and often at capacity
A screened private adopter	Fine, with questions asked	The screening is the whole job
A chain pet shop	Frequently declines	Policies vary by branch
A school, office or care home	Usually a worse home than yours	Nobody is individually responsible

Aquarist societies are the answer most people never consider. Almost every region has a club, many have a goldfish or coldwater section, and their members are exactly the people with a spare pond and the experience to use it. They will ask you sensible questions, which is a good sign rather than an obstacle. Most will help a non-member.

Pond owners are the right home for single-tails. A comet or shubunkin in a garden pond is in the life that breed was built for — goldfish ponds covers what a decent one looks like, which is what to check before handing the fish over. Fancies are a different matter and generally should not go outdoors.

On schools and offices: the objection is not the people, it is the structure. A tank that belongs to everyone belongs to nobody, it is unattended for holidays and weekends, and it gets fed by a rotation of well-meaning people who each assume nobody else has. If an individual at the school is taking the fish home, that is rehoming to a person and is fine.

Screening a new keeper

Not interrogation — five minutes of questions that determine whether this works.

What to ask:

• What is it going into, and how big? The single question that matters.
• Is it running now, and for how long? A cycled tank is a completely different proposition from one filled yesterday.
• What else is in it? Tropical fish, a single-tail with a fancy, or a predator all change the answer.
• Have they kept fish before? A first-time keeper is not disqualifying — goldfish for beginners is the page to send them — but it changes what you tell them.
• What is the plan when it grows?

What to tell them, without being asked:

• The full health history, including anything you treated and anything you never resolved. A fish with an undisclosed history becomes someone else’s outbreak, and a goldfish can carry a pathogen without showing it — goldfish diseases explained covers what travels this way.
• The parameters it has been kept at, particularly temperature and hardness, so the new keeper can match rather than guess.
• Its rough age and how long you have had it.
• What it eats, and how much.

And ask them to quarantine it. Any keeper worth giving a fish to will already intend to — quarantining a new goldfish is the page to send them.

What to send with the fish

Most of this costs you nothing and makes an enormous difference.

• A colonised sponge filter. The most valuable thing you can give. It lets the new keeper run a tank immediately instead of cycling one around a fish, and it is the difference between a smooth transfer and a month of ammonia. Keep it wet in tank water for the journey.
• Enough of your tank water for it to travel in.
• The food it is used to, or at least the name of it. Goldfish are conservative about new food and a change on the same day as a move is two disruptions rather than one.
• A written note. Temperature, parameters, age, diet, health history, anything it dislikes. Five lines on paper, and it is the thing new keepers say afterwards that they were most grateful for.
• Any medication history, in detail, if there is one.

Do not send the gravel, the old decorations or the ornament it liked. None of it helps and all of it is a disease vector into a tank that is not yours.

Writing the advert

If you are listing the fish publicly, the advert does most of the screening before anyone contacts you.

Say the size, honestly. “Goldfish” makes people picture something small. “Common goldfish, about 25 cm, needs a pond or 280 litres plus” removes everyone who was going to put it in a bowl, which is the entire point.

Say what goes with it. Tank, filter, stand, and especially a running sponge filter. This is what turns a difficult listing into an easy one.

Say what it needs, in one line: coldwater, no heater, a filtered tank of a stated size, and that it can live another decade or more. What keeping goldfish costs is a fair thing to link for anyone who has not done this before.

Include a photograph with something for scale. A fish against a plain background next to a hand or a ruler tells a reader more than three artistic shots.

Do not offer it for money. Free removes the incentive that produces the one response you do not want, covered next.

Two more filters that work: ask for a photograph of the tank it is going to, and say in the listing that you will. Both are entirely normal requests among fishkeepers and both end the wrong conversations quickly.

Timing

Rehoming has a season, which is not obvious and makes a real difference.

Spring and early summer are easiest. Ponds are being set up and stocked, clubs are active, and people are thinking about fish. A single-tail offered in April has several times the options it has in November.

Autumn is the worst time to send a fish outdoors. A goldfish moved into a cold pond in October has to adapt and then immediately overwinter, with no feeding window to recover in — the temperature bands in a pond through the year explain why that is a bad combination. Indoors is fine year-round.

Do not move a fish that is unwell, ever. Treat it first, or keep it. A sick fish travels badly and arrives as a disease problem.

And do not rush a placement because you have a deadline. A fortnight in a tub in the garage, properly filtered, beats a bad placement made in a hurry.

The unwanted fish you did not choose

A common route into this page, and it deserves its own answer.

A fairground or prize goldfish arrives with no tank, no warning and often in poor condition. Goldfish welfare takes the line that the fish in your hands is not the one to make a point with: take it, house it, decline the next one.

If you genuinely cannot house it, the first hours matter more than the placement does. Get it into a covered container of dechlorinated water at a stable temperature, do not feed it for the first day, and start the calls. A bucket with a lid and an air stone will hold a single small goldfish safely for a week — the hospital tank page covers improvising one at short notice, and the same improvisation works here.

An inherited tank — from a house move, a relative, a departing housemate — is the other version. Test the water before anything else, because a neglected tank is usually a water problem before it is a rehoming problem, and why did my goldfish die covers reading a tank you did not set up.

In both cases you have more time than it feels like you do. A goldfish in adequate water is not in an emergency, and a week of looking produces far better options than an afternoon of it.

Moving the fish

The same procedure as any other move, and the handling guide covers it properly. The short form:

Bag or bucket it in its own water, not fresh water. Keep it dark — a covered bucket or a bag inside a box — because a fish that cannot see movement stays calm. Do not feed it for a day before, so it travels with an empty gut and fouls the water less. Keep the journey short and the temperature stable. And let the receiving keeper acclimatise it, rather than tipping it in on arrival.

Rehoming part of a group

A specific case, and the choice of which fish to move is not arbitrary.

Move the fish that is causing the mismatch, not the one suffering from it. If a fast single-tail is outcompeting two fancies, the single-tail is the one to rehome, and it is also the one with the better onward options because pond owners want it.

Move the healthy ones, not the compromised one. A fish with a chronic problem is harder to place and travels worse.

Keep an eye on the ones that stay. A group re-forms after a departure much as it does after an arrival, and chasing and bullying covers what that fortnight looks like.

And re-check your stocking afterwards, because the point of the exercise was the numbers.

Giving up the tank as well

Frequently the easiest rehoming of all, and worth offering explicitly.

A fish that comes with its tank, filter and stand is a much easier thing to say yes to than a fish alone. It removes the cost barrier, it removes the cycling problem, and it removes the risk that the fish goes somewhere undersized.

It also gets the fish a better home, on average, because the person taking it is not improvising around what they already own.

Say so in the advert. “Goldfish, 180-litre tank, filter and stand, free to a keeper with space” gets a different and better class of response than “goldfish, free to good home”.

If nobody will take it

It happens, so it gets a section.

Keeping it is a legitimate outcome. A plain food-grade tub with a sponge filter and a lid is inexpensive, holds more water than most aquariums, and is a perfectly decent life for a goldfish. It will not look like the display you imagined. The fish does not mind.

Improve what you can, in the order set out in goldfish welfare: stop anything actively harmful, then feeding, then filtration, then volume.

Keep trying periodically. Societies get new members, ponds get built, circumstances change. A fish that was unplaceable in February is sometimes placeable in May, when people are setting ponds up.

And euthanasia belongs in this conversation only narrowly — for a fish that is genuinely suffering, not merely inconvenient or unplaceable. Humane euthanasia opens by saying that most of the time the answer is not yet, and that applies here with particular force. An unwanted healthy goldfish is a housing problem, and housing problems have housing solutions.

Taking one on

The other side of this, and increasingly common.

Quarantine it, whatever you are told about its history.

Ask the questions in this page’s screening section, in reverse. Age, parameters, diet, what it has been treated for.

Expect it to be larger than you were told, or smaller and stunted. Fish described as “small” have often been in a tank that kept them that way, and how big goldfish get covers what happens when one is finally given room.

Take the sponge filter if there is one, and ask if there is not.

And expect a settling period. New water, new light, new company, no familiar landmarks. Two weeks is normal.

The short version

Check whether the fish needs to move at all. If it does, try people you know, then a local aquarist society, then a pond owner or an independent shop. Ask what it is going into, tell them everything including the awkward parts, and send a colonised sponge filter with it.

Offer the tank as well if you can — it doubles the quality of the responses. And if nothing comes off, keep the fish in a tub and try again in spring.

The only option that is never available is the river.