Goldfish Care Sheet: Everything You Need to Know on One Page

When people think about keeping pet fish at home, the goldfish is definitely top of mind for most. That being said, proper goldfish care is not widely understood.

Now, I like to entice readers with interesting statistics. So, I tried to find out how many goldfish are kept as pets around the world. I failed, the number’s not out there and the best I could do is to tell you that more than 48 million Americans ate at least one bag of Pepperidge Farms Goldfish crackers in the past month.

All humor aside, while this doesn’t help us calculate the world goldfish population, it does speak to the popularity of them and the solid place they have in our collective consciousness. So the lack of knowledge around caring for goldfish properly is a cause for concern.

This article will take care of that.

Two orange goldfish in front of some aquatic plants

In this one page care sheet, this complete step-by-step guide on how to care for goldfish, we’re going to give you everything you need to meet all of their needs.

Along the way, we’ll dispel a few myths, let you know what equipment you need, detail how to set up a pet goldfish tank (yes, tank – never a bowl!), how many goldfish you can keep at once, tips on buying healthy specimen, as well as daily, weekly and monthly maintenance tasks and more!

Keep reading and get ready to enter the wonderful world of caring for goldfish.

The Bottom Line up Front: Goldfish Care Guide Checklist

The below is just a goldfish care summary, a quick checklist that covers the very, very basics, before we expand on everything further into the article.

Tank Size – Depends on variety, and how many you keep together:

  • Fancy goldfish (such as black moor, fantails, oranda and telescope eye): 20 Gallons plus 10 for each extra fish.
  • Single tail goldfish (such as common goldfish and comets): 30 to 40 gallons, plus 10 gallons for each extra fish. Though they do much prefer ponds!

Don’t even consider keeping goldfish in small bowls. These are reserved purely for the world of cartoons, not for actual living beings. We will never recommend goldfish bowls on this site, they are always way too small! You CAN keep goldfish in larger bowls, but it requires a very special skill set, is not for beginners and we do not recommend it.

Substrate – Large gravel or aquarium sand are recommended as best. Avoid a bare bottom as goldfish like to dig and forage.

Filter – All goldfish aquariums MUST have a filter (except for rare circumstances, for very experienced goldfish keepers). Aim for a filter with a rating that will turnover 6x to 10x per hour the water volume in your tank.

Water Temperature – Ideally between 65-74F (18-23C)

Water quality and parameters – You MUST use a water conditioner to remove chlorine and chloramines from tap water before adding to your tank. And you should purchase a freshwater chemical testing kit, and aim for the following water parameters to maintain good health:

  • pH – 7.2-7.6
  • Ammonia – 0 ppm
  • Nitrite – < .25 ppm
  • Nitrate – < 30 ppm

Lighting – Goldfish thrive with a day and night cycle, much the same as we do. So try to ensure they get it. Natural light will suffice, but artificial light during the day, and tank covered during the night is better.

Plants and Decorations – Goldfish love an enriched environment. Add live plants, or if artificial, make sure they are soft and silky to avoid ripped fins, particularly with fancy goldfish. Ornaments they can hide behind, swim through and under are also appreciated.

How many goldfish to keep together? – They are a communal fish and like company, though can be kept alone. 3+ is ideal. But do not mix fancy goldfish and single tail common goldfish or comets in the same tank, the fancy goldfish will be outcompeted and may not thrive.

Goldfish diet: How much and what to feed them? – Feed specially formulated goldfish flakes or pellets, 2 or 3 times per day, as much as they can eat in 2 minutes before removing uneaten food. Also vary their diet with occasional (once per week) bloodworms, shrimp, watermelon, shelled peas, kale, chard, or cucumber.

OK, so that’s the bare bones summary 🙂

From here we go into far more detail on all of the above points and more, including preparing and setting up your first goldfish tank, introducing your goldfish to their new home, and suitable mates for them to live with, as well as padding out the above checklist with reasons, so you can feel confident you know WHY you are doing something, as well as how.

Let’s get to it!

It all Starts With the Right Tank, Equipment, and Accessories

Photo of a local fish store shelves and aisles

If you are planning to get your very first goldfish – which for many readers will be the case – then you need to have your tank already set up, pre-cycled (more on that later) and ready to receive your new friend.

So instead of starting this guide with how to choose a good and healthy goldfish, we’ll start with setting up their home first. And that begins with a visit to your local fish shop.

Walking into an aquarium store can result in sensory overload. There are so many tanks, filters, decorations, and other stuff it can be tough to pick out the gear that you need.

Let’s quickly pare down the choices and get to what is essential.

Choosing the Right Tank

Buying an aquarium for fish is a little like buying a home for yourself; you have to pick one that meets your needs, both present and, if possible, future. But while keeping an eye on the cost and what you can afford.

Our advice is: Buy the biggest tank that you can afford and have ample space for in your home.

Obviously, within reason! Don’t go overboard. We’re not saying to buy one that takes up a whole room if you have 7-figures in the bank!

But the reasons we say to go as big as you can are three-fold:

  • The bigger the tank, the easier it is to maintain a healthy ecosystem. Counter-intuitively, larger aquariums require less work from you to keep them in good health, less monitoring, fewer water changes and so on.
  • Goldfish like a lot of room. The bigger the tank, the happier and healthier your goldfish.
  • A larger tank gives you more options to add live plants, ornaments, further goldfish, or community fish in the future if you wish to.

A smaller tank is harder to maintain, will require more water testing, water changes, more effort and skill from you to keep things running smoothly, as well as limiting any possibility of expanding what else you can put in there. So…go large!

But what is the minimum size we recommend?

The Rule of Thumb for Minimum Goldfish Tank Size

It depends on the types of goldfish you plan to keep:

  • Fancy Goldfish Varieties: 20 gallons of water for the first fish, plus 10 gallons for each additional fish
  • Single Tail Varieties: 30-40 Gallons of water for the first fish, plus 10 gallons per additional fish

Why such a big difference in tank size?

Single tail varieties, like comets or common goldfish, have the potential to grow quite large, often as long as 12 inches! They are incredibly active, swimming fast and often. They’ll need extra room to move around comfortably, both vertically and horizontally.

If you think you’d like a small school of single tails, maybe 4 or 5 total, you’ll need at least a 70-80 gallon tank. For this reason, many fish-keepers see single tails as more suitable for ponds.

In comparison, fancy goldfish varieties (those that are more egg-shaped with double tails) don’t grow to be so long, are far less agile, swim less and slower, and hence are happy in a slightly smaller environment.

If you don’t know the difference between the many different varieties of goldfish, please check out our guide to the different goldfish types.

So, before you buy a tank, think ahead to how many fish you’d like to keep, and what variety. Consider not only goldfish but also any other fish or plants you might want to include one day. (Note: We’ll talk about suitable companions a little later in this article.)

Note: You can check out this guide for more details on goldfish tank size requirements.

The Right Substrate for Goldfish Tanks

A photo montage of 2 types of aquarium gravel and sand

Substrate is, appropriately, the blanket term for whatever material you choose to cover the bottom of the tank. There are many choices available, including using nothing at all.

So which substrate is best for goldfish?

First off, we almost always suggest using substrate of some type in your decorative tank, no matter what kind of fish you’re keeping.

Substrate is a breeding ground for bacteria – but don’t be alarmed, it’s the good kind and we need it!

Good bacteria are an essential part of the nitrogen cycle, which we’ll also talk more about later. There are some advantages to having (ahem) a bare bottom, such as being easier to clean, but goldfish prefer it covered up.

This is because goldfish are natural foragers, they like to dig and root around in sand, gravel, soil or anything, looking for morsels of food. It’s a natural behavior, so we should always try to set a tank up for this.

The type of substrate you choose depends on two factors: the fish you plan to keep, and whether or not you want to grow live plants.

Your two basic choices of substrate for goldfish tanks are sand or gravel.


Gravel has many advantages as a substrate. It vacuums easily so is easy to keep clean, and it has lots of surface area for bacteria to thrive, keeping your tank healthy. Goldfish love to forage and root around in substrate, and gravel is very well suited to this behavior.

If you want to have live plants, gravel is ideal for laying down solid roots. It looks great, too, and you can mix and match a variety of colors.

Be sure to use only gravel specially packaged and sold for aquarium use, but avoid the smaller stuff typically known as pea gravel. Goldfish continually pick up gravel in their mouths if they can, and pea gravel is just the right size (wrong size) to get stuck in their mouths and be a choking hazard. So make sure gravel has an average size of 1cm to 2cm across. It may be harder to find, but it’s safer.

Also, make sure it’s labelled for aquarium use, because other types of gravel could leech undesirable minerals and chemicals into your aquarium water. Also make sure it has no sharp edges, to avoid possible tail and fin damage.


Perhaps the most natural looking of all substrates, aquarium sand can yield beautiful results. It’s easy for fish to root through, though anecdotally some say it can irritate their gills. I am of the opinion, however, that sand is just fine for goldfish.

The downside to sand is that it’s much harder to keep clean. It’s difficult to vacuum without sucking some up, and because it’s so compacted, it doesn’t aerate as thoroughly as gravel. This can lead to trapped pockets of hydrogen sulfide that, if they release into the water, are extremely toxic. Your best bet is to stir up the sand regularly to aerate and release any trapped gasses.

As with gravel, only use packaged sand especially for aquariums. You might be tempted to save some money and use sand from a nearby beach or leftover play sand from a child’s sandbox, but both of these pose serious potential threats to the health of your fish.

Ultimately, the great substrate debate comes down to a matter of personal preference. I’ll give gravel a slight edge, but you can’t go wrong either way.

Must you Buy a Filter? If so, What Type Should You Choose?

Close up of an internal fish tank filter

Because we’re so used to seeing goldfish in bowls, many people think they don’t require a filter. Not the case! With few exceptions, all goldfish tanks should have a filter.

Goldfish are prodigious poopers. Like many species of fish (and interestingly, the platypus!) goldfish do not have stomachs. What they eat goes straight into the intestines where available nutrients are extracted and then it’s right out the backdoor. That means without a filtration system your fish will be swimming in its own waste in no time, a sure recipe for a short life.

So the answer is, yes, your goldfish needs a filter. But which type is best?

To start with, it must be a powered filter to keep up with your goldfish’s bathroom habits. From there you have two choices: internal or external.

Internal Filters

You don’t need an advanced degree to know that an internal filter goes inside your tank. Constantly running, the filter draws water up and through a filtration medium and then expels it back into the tank.

Large particulate is trapped in the filter, and good bacteria work on breaking down harmful chemicals into something more benign. The filtered water is expelled back into the tank, and all you need to do is occasionally rinse out and/or replace the filter medium.

Internal filters are practical in that there’s nothing outside your tank except the power cord. This allows your tank to occupy the minimum possible footprint. On the downside, they occupy valuable internal “real estate” and they generally look ugly. They are also limited in size and capacity.

External Filters

Naturally, this type of filter operates outside the tank. Water drawn through an uptake pipe enters the filtration system where, just like in an internal filter, it goes through filtration medium (sometimes multiple kinds) and is then returned to the tank.

They take up space outside the tank, so you’ll need to leave them some room on the shelf, stand, or table, though most aquarium stands and cabinets have space within them to keep external filters wholly hidden beneath and out of sight.

On the bright side, they have a minimal impact on the internal aesthetics of your aquarium, and it’s pretty easy to hide the pipe with plants and decorations.

Our Recommendation

If you have space, go with an external filter. They are almost invariably better at cleaning than internal models and have higher capacities for collecting waste and holding friendly bacteria.

Since, as we’ve said, your goldfish make a lot of waste, it’s essential to have a filter that can keep their water suitably clean.

Look for a filter with a high flow rate – figure on 6-10 times the volume of water in the tank per hour. That means for your 50-gallon tank, you want a filter with a flow rate of 300-500 gallons per hour.

Check out this article for a more detailed discussion: Do goldfish tanks filters.

Goldfish Water Temperature: Using Heaters and Thermometers

aquarium thermometer isolated on white

Goldfish can tolerate a surprisingly wide temperature range. Ideally, you want to keep goldfish water temperature anywhere between 65-74F (18-23C) and try to avoid survivable but undesirable extremes.

For many people, this means a heater isn’t necessary since goldfish like room temperature water. If you know the ambient temperature in the room will stay within these parameters, you won’t need a heater.

If your home dips below the bottom of the range, seasonally or just because it’s always cold where you live, you will need a heater. Heaters are great for maintaining a suitable constant temperature.

Whether you do or do not need a heater, a thermometer is a must-have. This is the only way for you to be sure that water is in the right temperature range. It’s a low-cost investment and just one of the many ways to keep tabs on your goldfish’s home.

Water Conditioners – Tap Water MUST be Treated

The most basic tool you’ll need for having safe water is a good water conditioner. You mustn’t merely fill up your goldfish tank with tap water. You need to treat it first.

All water companies treat their water before pumping it to our houses, to make sure it’s fit for human consumption. However, this means it contains chlorine and chloramines that are highly toxic to fish. So you have to add a water conditioner to remove these before the water gets anywhere your goldfish.

Our favorite water conditioner is this one from Seachem. This is primarily used for dechlorinating, but also detoxifies ammonia, nitrite and removes heavy metals. All good things for your fish.

Simply follow the instructions on the bottle, there’s nothing more to it 🙂

Cycling your Tank

There’s one more thing you need to do once water is added to your tank before you can introduce your fish, and that is to ‘cycle your fish tank.’ Skipping this step may result in seriously ill or even dead fish. Or you having to change the water religiously almost every day. Here’s why…

When fish poop, it rots and adds ammonia to the water. Ammonia is highly toxic, and can literally chemically burn your fish alive in high enough doses.

A fish tank is a closed system. There is no water in or out. What’s in there stays in the there, including all your fishes waste and nasty chemicals that come from it.

There are two ways that chemicals are removed from a fish tank, which work in harmony:

  1. The nitrogen cycle.
  2. Frequent water changes

Water changes are obvious and we’ll come back to this later, but the nitrogen cycle needs some explanation.

A diagram of the nitrogen cycle and how to cycle a fish tank

When fish produce waste, ammonia is created in the water. In an established – or cycled – tank, there are friendly bacteria in the filter, on the substrate, and on every surface of the inside of the tank, that feed on the ammonia and produce much safer chemicals called nitrites.

But nitrites are also toxic!

Luckily for us, other friendly bacteria feed on the nitrites and convert them to nitrates.

Nitrates are far, far safer than ammonia and nitrites. So the ‘friendly bacteria’ you keep hearing me mention, convert toxic ammonia and nitrites into far more harmless nitrates.

Then, when the nitrates have built up to unsafe levels, we as fish keepers perform a water change to remove to the nitrates.

Us and the friendly bacteria make a damn good team!

However, in a new fish tank, there are no friendly bacteria! It takes time for them to establish themselves. And during their absence, if any fish are present producing waste, ammonia and nitrites run rampant, and your fish are slowly being poisoned.

So at the start of a new tanks life, you need to perform what’s known as a ‘fishless cycle.’

A fishless cycle is you establishing the vital bacterial colonies without your fish being present so that when your fish are added, their waste is converted into safer chemicals instead of poisoning them, leaving the water fit for them to live in.

The nitrogen cycle and ‘fishless cycling’ are beyond the scope of this introductory guide, so please check out my guide to cycling your fish tank. Seriously, go check it out! It’s super important.

Water Quality and Parameters

Next, you’ll want a testing kit, to check for chemical levels in the water.

Many people believe that if the water looks clean, then it is. The filter removes all the waste and gunk, the water looks clear, everything’s fine and rosy. But this is certainly not the case!

Water can be crystal clear, but full of fish killing toxic chemicals, and the only way to detect this is with a water test kit.

You can purchase test strips, chemical kits, or reusable digital testers. Either one will tell you what you need to know about pH, chlorine, nitrites, nitrates, and hardness, but some kits are better than others.

The freshwater API master test kit is my preferred. Paper strips, though cheaper and easier to use, are notoriously known for being inaccurate  The API master test kit is a chemical kit that is accurate, still relatively easy to use, and will last a long time.

We cannot stress enough how you MUST buy a testing kit. If you happen to own a swimming pool, you know it’s essential to maintain clean water with optimal pH, chlorine levels, and so on. And that’s just for swimming; imagine if you had to live in the water!

And so it goes, there are water quality requirements for keeping healthy goldfish.

Yes, they can put up with some fairly nasty conditions. But they won’t thrive in those conditions. Here are the numbers you need to be concerned with:

  • pH – 7.2-7.6
  • Ammonia – 0 ppm
  • Nitrite – < .25 ppm
  • Nitrate – < 40 ppm

You should test your water regularly. If nitrates creep over these figures, the immediate fix is a partial water change.

If ammonia or nitrites creep over these figures, an immediate water change is also needed, but there may be something wrong with the bacterial colonies, so constant monitoring and perhaps further action will be required. This is thankfully rare though.

Lighting Needs for the Care of Goldfish

Do goldfish need light written above 2 goldfish swimming in a light bulbTry having a staring contest with a goldfish. Did you blink first? Of course you did – they don’t have eyelids!

That right there should tell you that to sleep properly, they need the lights off at night. Likewise, they like it bright enough to see clearly during the day.

For some people, the natural cycle of day and night may be enough to get away without installing artificial lighting. For most, however, that’s not the case. And, even if it is, there are advantages to lighting your tank.

For one thing, you can control the light/dark cycle and keep it consistent year round. If you happen to live in the north and you want to see your fish after p.m. during the winter, a light is essential!

Also, lights can really make the colors of your beautiful goldfish pop! Why relegate these dazzling golden beauties to a life of perpetual dusk when they could be shining? Not only will your fish look better, but your plants and decorations will too. Good lighting is one of the keys to creating a wonderful looking aquarium.

Check out the following guide for a far more detailed look into the question: Do goldfish need light?

Plants and Decorations

Goldfish are curious, active fish, and they love an enriched environment. I highly recommend adding decorations for swimming through and around, and for hiding behind when they’re feeling a little shy.

Take a moment to explore anything you’re planning on putting in your tank with your fingers, first. Feel around for sharp edges that could tear your goldfish’s fins, especially if you are keeping any fancy varieties.

The same goes for plants; either use live ones or soft, silky artificial ones, but NEVER hard plastic ones.

If you do wish to add live plants – and I recommend you at least try some of the hardier ones – the following are great varieties for both Goldfish and beginner aquarium plant keepers:

  • Anacharis Bunch
  • Duckweed
  • Hornwort
  • Water Sprite, aka Indian Water Fern
  • Amazon Sword
  • Anubias Barteri
  • Java Fern
  • Parrot Feather
  • Cryptocoryne
  • Water Wisteria

Setting up Your Tank

OK, so now we have all the knowledge and maybe the right equipment, let’s throw it all together, fill the tank with water, insert the fish. Right? Very wrong!

I know you’re excited to start enjoying your goldfish, but before you bring your fish home, you first have to set up their tank. It’s kinda like cleaning out a house and repainting it before people can move in. Only with fish, it can be a matter of life and death.

Here are the proper steps to get your tank set up and ready for moving day!

Initial Tank Preparation

No matter if it’s a used tank or brand, spanking new, the first step is always to clean it out thoroughly. You never know what kind of contaminants might be lurking inside.

A new tank probably just needs a good rinsing and a wipe down, both inside and out. Do the same for any equipment it came with that’s going to be in the water.

If you’re recycling a used tank you’ll want to do a more comprehensive job to be sure it’s inhabitable and safe, that it’s disease, chemical and parasite free.

Remember never to use any soap, detergents, or chemical cleaners inside an aquarium!

Leaving behind even the tiniest bit can harm or even kill your fish.

Adding Your Substrate

No matter if you’re starting with fresh substrate or reusing old stuff, you’ll still need to rinse it before use.

For gravel, pour it a bit at a time into a colander and rinse it thoroughly and repeatedly under hot water before adding it to the tank.

PRO TIP: It’s a good idea to buy a colander especially for this purpose to avoid any possibility of cross-contamination.

Sand also needs to be rinsed, but it’s too fine for a strainer. Instead, put sand in a bucket and then add water. Slosh the sand around to rinse it and then let it settle to the bottom. Once it’s settled, you can carefully pour out the water, and then add the sand to your tank.

Installing the Filter

Now you’re ready to set up the filter. This is an essential part of your aquarium system, and it needs to be ready to roll when you add the water.

Some models can be a bit tricky to install, even with the instruction sheet. Our suggestion: try and find a YouTube video of someone assembling and firing up the same kind of filter.

If you’d prefer to read rather than watch, here’s a link to a really great article explaining how to set up five common types of aquarium filter. You’ve got this!

Warning: Never turn on a filter until the tank is full of water. Running a filter dry is an express route to a ruined filter.

Adding a Heater

If you’re going to use a heater in your goldfish tank, now is the time to install it. By placing it now, you’ll be able to add plants and other decorations to hide it easily. Most likely, you’ll position the heater somewhere towards the back where it’s less visible. Carefully place the power cord so that the tank cover doesn’t pinch it.

Warning: As with the filter, it’s important to leave the heater off until the tank is full of water. Using a heater without water can damage the element, or in some models, can even cause the glass housing to explode.

Adding Plants and Decorations

A heavily planted aquarium landscape

The next best thing to finally adding your new fish is setting up the plants and décor. Placing everything while the tank is still dry makes it much easier to play with positioning until you’re satisfied.

Before anything goes in, make sure to rinse each item thoroughly. You can even scrub them with a soft brush, but do not use any soap. Soap residue is not something you want in aquarium water.

As you’re putting things in place, give some thought to the needs of your goldfish. Set up places where it can go for a little privacy and nooks and crannies for exploring. Make sure not to overcrowd the tank, however, and leave them enough room to move around freely.

Artificial plants that float or require water to stand upright may be easier to add after the water is in. This allows for more precise arrangement. You can add live plants after you’ve partially filled the tank to keep their roots moist at all times.

Adding Water and Treating it for Safety

At this stage, you’re all set to fill up your tank with water. More than likely you’ll be using tap water, which is treated to be safe for human consumption. However, as discussed above it is not fit for fish to live in.

This means you’ll need to use a water conditioner (you can buy it online or at any pet or aquarium store) to neutralize chemicals like chlorine that may be present.

Unless you can run a hose to your tank, the easiest way to add water is to repeatedly fill a bucket and then pour it in. Try to pour carefully so as to disturb the substrate and decorations as little as possible.

What if I Have Well Water?

Though you might think well water is close enough to natural to be safe for your goldfish, you should still treat it with water conditioner.

Well water may contain minerals, heavy metals, and runoff pesticides that are unsuitable for fish. Even if it’s run through a filtration system before exiting your faucet, it should still be treated.

Make Sure Your Tank is Cycled 

There’s just one last stage before your tank is ready for fish to move in.

I know I mentioned this in some detail above, but it’s so important – and so many people either ignore or skip this step –  that I’m going to stress it again.

Though you’ve cleaned the water with conditioner, the system needs to be prepped and ready to deal with the incoming fish waste by establishing colonies of helpful bacteria. This is called “cycling the tank.”

For the complete story on how and why you need to establish a nitrogen cycle, please read our comprehensive article on how to cycle a fish tank. Please, do go read it. It is soooo important.

And just remember, it may take days or even weeks before the water is ready for fish. But be a good owner and go through the process.

OK, all cycled? It’s time to add some fish!

Buying and Adding Your Goldfish to the Tank

Orange goldfish in aquarium with plants and stones

The best part is here! Time to go out and choose your goldfish and bring them home. To help you make the best choice, here are some factors to consider and signs to look for.

Should I Buy Males or Females?

Unlike with some species, like bettas, it isn’t strictly necessary to separate your goldfish by gender.

The males are unlikely to be a threat to females or each other. In terms of attractiveness, males are sometimes a bit showier than females; their bodies might be slightly smaller, but the fins are often larger.

It can be extremely difficult to tell males and females apart, even for experienced aquarists. The easiest way to determine gender is to wait for breeding season. This happens naturally during the spring, but the conditions can be artificially created in a tank to force breeding.

Males will start to show breeding tubercles along their gill covers and by the pectoral fins. The tubercles look like small white dots and are quite distinct.

Outside of breeding, or spawning season, you may be able to recognize a male goldfish by a large ridge running from the back of the pelvic fins to the vent. The vent is the opening through which males release sperm and females release eggs.

Ultimately, it doesn’t really matter whether your goldfish are male or female unless you plan to breed them. Ask at your aquarium store for help selecting the gender of your choice. Even if you do get a mix, however, it may not lead to unwanted babies. They won’t breed unless the conditions are just right.

How Many Goldfish Can I Keep?

They are social fish and will thrive in the company of others of their own kind. How many you can keep at once is only limited by the size of your aquarium. Remember the rules we gave earlier?

Make sure not to keep a mix of single tail varieties and fancy goldfish in the same tank, though. The single tails are more aggressive, perhaps from being genetically closer to their wild carp family relatives, and will out-compete the fancies for food.

Making Sure You Pick Healthy Fish

Buying a fish and bringing it home, only to have it die within a short time is very frustrating. This is especially true when you know you did everything right with your tank.

Often what happens is the fish came home sick. Starting with a healthy goldfish can save you from disappointment.

For your best odds at choosing a healthy fish go to a breeder or a knowledgeable aquarium store rather than a general pet store. From there, it’s all about observing the fish for certain tell-tale signs of goldfish illnesses and sickness.

First, look at the conditions of the tank. Is it dirty? Overcrowded? Are there dead or sick looking fish that haven’t been removed? These are all indicators that the environment isn’t healthy, and therefore the fish may not be either.

Check for physical signs of an ailing goldfish. This includes looking for torn fins, swollen eyes, white spots, clamped fins, and lethargy.

Is the fish active and energetic? You want to choose goldfish that are bright and shiny, actively swimming around upright continuous at a comfortable pace, aren’t floating on their sides or upside down, or resting at the surface or bottom of the tank regularly.

If you can tick all the above boxes, then you can avoid purchasing an unhealthy fish.

And when you do choose your fish, don’t forget to name them using our list of 634 fun and interesting goldfish names!

Adding Your Goldfish to the Tank

Introducing new fish from a bag into an aquarium

At long last, we’ve reached the moment you’ve been working towards! The tank is ready, and your healthy fish are home. Time to move them in!

Hold up there, cowboy – you can’t just open the gate (or bag, in this case) and set them loose. You run the risk of shocking your new fish and adding any contaminants that hitched a ride from the aquarium store. I’m pretty sure this is how I once ended up with snails without buying any.

Quarantine Your New Goldfish

It’s highly recommended to quarantine any new fish in a separate tank and to treat them for common diseases and parasites, before adding them to your main aquarium.

This is especially important if your tank already contains some existing fish.

A large number of fish bought from pet stores harbor disease. They may not look it, but they do. They may look healthy when you bring them home, but it could be just that any illness or parasites are in the early stages, or that the fish has been strong enough to keep the sickness and symptoms down.

However, the drama of being bought, stuffed into a bag, driven around, and finally brought into a new environment causes a lot of stress and can result in a temporary drop in a fish’s immune system. And at this point, any illnesses can come to the fore and take over.

The last thing you want to do is introduce this fish into your main tank, particularly if you have existing fish as it will make them all ill, or the new fish could catch something from the others while weak from stress.


Any new fish you bring home, temporarily home them in a separate quarantine tank, and treat them for common goldfish diseases to make sure they are healthy before adding them into the main tank.

A complete quarantining guide would add a couple of thousand words to this already lengthy guide, and so is outside of the scope of what I can add here. Therefore, please go read and put into action the advice in this guide to quarantining goldfish from

Acclimate Your Fish Before Adding to their Final Home

So you’ve bought the perfect fish, and have quarantined them so you’re sure they are fit and healthy? OK, let’s move them into their new and final home.

Here’s a summary of the steps to follow when adding new goldfish to a tank:

  1. Switch off the aquarium lights (the fish will be too close.)
  2. Float the sealed bag in the aquarium for 15-20 minutes.
  3. Open the bag and roll down from the top several times, taking care not to let water get from the bag into the tank.
  4. Scoop or otherwise drain 1/4 of the water from the bag.
  5. Using a clean cup, add a small amount of aquarium water to the bag and reseal it.
  6. Repeat steps 3 to 5 a couple more times over the next hour. The reason we do this is to slowly acclimate the fish to the new water parameters, particularly the pH.
  7. Finally, carefully capture your goldfish with a net or your hands, and gently place it in the tank.
  8. And just to reiterate: NEVER POUR THE BAG WATER INTO THE TANK. Especially true if pet shop water, but also true of water from your quarantine tank.

Moving your goldfish to their new home correctly is a crucial step. If you just dumped them straight in they could suffer from shock due to the change in water temperature and pH levels. This can make them ill. So take the time to add them correctly.

To learn more about how it should be done and a couple of other methods, we highly recommend reading our complete guide to introducing new fish to an aquarium.

Food and Feeding Routine For the Best Goldfish Care

Feeding goldfish is more complicated than simply dumping in some flakes and hoping for the best. It’s important to know what an appropriate diet is and to understand how they eat.

Are they herbivores or carnivores? Bottom feeders or surface feeders? Read on for the answers!

What do They Eat?

How to feed your goldfish written beside a cartoon fish carrying a plate of chipsOne of the reasons goldfish are such hardy survivors is they’ll eat just about anything. Like us, they are omnivorous creatures, meaning they’ll eat both meat and vegetables to have a balanced diet. And, like some of us, they are voracious eaters, too!

The easiest way to ensure they get the proper nutrients is to feed them specially formulated sinking pellets for goldfish.

Sinking pellets are the most highly recommended staple food because as they sink, they prevent goldfish gulping down air from the surface – which can lead to swim bladder issues –  and also encourages the natural behavior they enjoy of rooting around the bottom looking for food.

Goldfish flakes are NOT recommended. They are usually low quality, too quickly dissolve into and pollute the water, as well as tend to float which causes goldfish to gulp down air, resulting in swim bladder issues and constipation.

As far as treats go, they will happily munch on anything from brine shrimp to bloodworms. You can also give them leafy green vegetables like kale, chard, and spinach, as well as broccoli, corn, shelled peas, and cucumber.

For fruit, you can offer watermelon, orange, and peeled grapes. Make sure to remove uneaten portions after a couple of hours to avoid fouling your tank. Treats should be restricted to just 1 or 2 times a week.

Since they’re indiscriminate eaters, take advantage of that to enhance both the health of your goldfish and their lifestyle. Vary their diet rather than sticking to a single food source. Not only will this provide a variety of nutrients, but it will also make life more interesting for your goldfish.

How Much and How Often Should You Feed Them?

In the wild, they eat a lot, but they burn it all off since they’re so active. Your average aquarium dweller though is somewhat more sedentary, so he or she requires fewer calories.

The problem is, goldfish are voracious eaters. They will eat…and eat…and eat…

This often leads to overweight fish, and problems with constipation and other digestive issues. So you really must limit the amount you feed them.

Feed your goldfish 2 or 3 times a day, but only small quantities.

A good rule of thumb is to offer as much food as can be eaten in about two minutes, before removing anything that is uneaten. More than that and you risk either overfeeding your fish or polluting the tank with rotting food.

If you’re not home for very long stretches during the day, you might want to invest in an automatic fish feeder to be sure your tank buddies are fed on a schedule and are given the right amount.

The following guide takes a deep dive look into what and how to feed your goldfish.

Maintenance – Daily, Weekly and Monthly Tasks in the Care of a Goldfish

Nothing worth having comes without a bit of work! Here are the tasks you can expect to perform on a regular basis to keep your goldfish healthy and happy.

Regular Water Changes

Regular water changes are super, super important!

As discussed above, Your fish produce waste, pooping in the water they live in. There is also uneaten food that rots in the water (you can never remove it all.)

The filter does a good job of taking out most of the solid particles and houses bacteria that convert some nasty chemicals into safer ones, but you still need to perform water changes REGULARLY to remove nitrates that build up, and that have no other way of being removed from the tank. (Caveat: Live plants do use up some nitrates, but it will almost certainly still build to unsafe levels in the vast majority of aquariums.)

So, although below, we recommend a partial water change weekly, what you must do is check the ammonia, nitrite, and nitrate levels weekly.

If all is well in your tank, ammonia and nitrites will be at or extremely close to zero. Bacteria eventually convert these into Nitrates. But nitrates only way out of the tank is via you and a water change.

Always keep your nitrate levels below 30 ppm (parts per million.) And under no circumstances ever let them go higher than 40 ppm.

How often you perform a water change will depend on so many factors, such as the size of your tank, how many and what species of fish live there, whether you have live plants, the food you put into the water, and more. So there’s no ‘one size fits all’ answer.

When testing your water parameters, if the nitrate levels are staying stable and below 30 ppm, then all is good. If they are increasing, then you must increase how often you perform a partial water change.

It could mean having to change water once per week, once per fortnight, or every 4 or 5 days. Only the nitrate levels can tell you.

Bt, what other tasks do you have to perform? Here’s a daily, weekly, and monthly checklist.

Daily Tasks

  • Feed your goldfish (2-3 times)
    • Make sure everything is being eaten to avoid waste build-up. Remove uneaten food after 2 minutes.
  • Inspect heaters, lights, pumps, and filters for functionality
  • Monitor the water temperature to be sure it’s between 65-74F (18-23C)
  • Look for signs of stress or disease
    • Abnormal behavior like erratic swimming or scratching themselves on rocks and decorations
    • Check fins for damage
    • Look for white spots, red sores or fungal growths

Weekly Tasks

  • Test water for pH, nitrites, nitrates, bacteria etc.
  • Use a vacuum to remove waste from substrate (this may vary – it might need cleaning more or less often)
  • Replace 20% – 50% of the water during weekly water changes. After the water change, retest it to make sure ammonia, nitrite and nitrates are at safe levels. If not, perform a further water change right away to remove some, and change water more frequently going forward.

Monthly Tasks

  • Clean your filters and replace any media if necessary
  • Trim any live plants getting too big
  • Remove and clean all decorations, artificial plants, rocks, etc.
  • Scrape or wipe excess algae from walls
  • Wipe clean lighting covers (algae and hard water scale build up over time)
  • Review food, medicine, test kits, etc. for expiration dates and throw out anything expired

Goldfish Tank Mates and Compatibility With Other Fish

They are generally sociable fish that get along, or will at least not bother many other types of fish. However, as we said before, do not mix single tails with fancies.

Aggressive species of fish should be avoided, like bettas and cichlids. This is especially true if you’re keeping fancy varieties; those big, beautiful tails are easy targets for fish that like to nip.

Here are a few species of aquarium fish that make ideal tank mates for goldfish. It’s by no means a complete list, but it’s a good place from which to start.

  • Rosy Barb
  • White Cloud Mountain Minnow
  • Weather Loach (or Dojo Loach)
  • Zebra Danio
  • Plecos
  • Apple Snail
  • Ghost Shrimp/Red Cherry Shrimp
  • African Dwarf Frog

Remember, there’s more to it than just social compatibility. Goldfish prefer cooler water than many tropical fish. So, while a breed of fish might be marked at the aquarium store as “community” fish, they also have to tolerate the same water conditions.

We also have an article looking at the best goldfish tank mates.

Final Thoughts

If you’ve only ever thought of goldfish as a short-lived creature bought for kids or won at fairs and then deposited in a bowl at home, this article may have been an eye-opener for you.

The truth is, goldfish, clichéd though they may be, are beautiful fish and can be very fulfilling for aquarists of any skill level. We hope that this is the start of a long and wonderful relationship.

Maybe you know someone thinking about bringing home a goldfish, or someone who already has one, but is unknowingly not taking proper care of it? Do them and their fish a favor – send them the link to this article. The more owners who know what it really takes to care for a goldfish properly, the better.

Thanks, as always, for hanging out with us today. Hopefully we’ve answered all your burning goldfish questions. If we haven’t, please take a minute to fill out our handy contact form or send us an email with your questions or comments. We will do our best to get you an answer in a timely manner!

Until next time, happy fish keeping!

External Resources on Goldfish Care

Recommended site no. 1: We recommend for it’s detailed, comprehensive and information rich articles. It’s well written, accurate, and good for beginners getting a handle on things as well as more experienced to level up their game. It’s also fun, written in a jovial style with lots of goldfish animations rather than photos:

Recommended site no. 2: Is good for general aquarium set-up and on-going care, with lots of short yet information packed articles: Aquatic Articles

Recommended site no. 3: We recommend because it has lots of fantastic information on types and their individual care requirements, common diseases and cures, tank set-up and more besides on goldfish keeping: Sitemap

Happy fish keeping!

Wendy Kathryn

Hi, I'm Wendy, the owner and creator of this website, an experienced fish keeper and avid student of the art since 2010. My aim is to help beginners avoid the many possible mistakes when getting started in this wonderful hobby.

6 thoughts on “Goldfish Care Sheet: Everything You Need to Know on One Page”

  1. Avatar

    Hi I’m hoping someone can help me, one of my goldfish the round belly fancy tail was getting picked on and floating sideways and upside down so I put him separate in a breeder tank in the big tank gave him 3 peas which he wouldn’t eat but ate r e g food, next day was not floating, put him back in tank and they attacked again so put back in the breeder and waited a couple more days and put him back and they all fine now a week later he’s floating upside down and they’re attacking him again and now I see a couple of white spots on him

    • Wendy Kathryn
      Wendy Kathryn

      Hi Lynn,

      What are the other fish that are attacking? And what are the ‘white spots’? Please have a google for ‘ich on goldifsh’ and click ‘images’ to see if they are similar to what you see and if so, treat for this.

  2. Avatar
    Gerard M. Ricci

    Hello – I am relatively new to the Hobby of Fancy Goldfish. I have four(4) Goldfish. One(1) I ordered from a store in New Hampshire – I asked for a Butterfly Tail. When it came in – The owner called it a “Round Body Butterfly”. Ok, Ok – ??????? It has a flat body, but has signs of a belly. I thought it was a Jikin, but it’s Gold and Black Calico. It’s a Beautiful Fish – I have no clue what it is – I would love to send you some Pictures to help with the ID

    Thank You for your Time
    Gerard M. Ricci

    • Wendy Kathryn
      Wendy Kathryn

      Hi Gerard,

      You can take a look through our guide for the different types of goldfish here: Different types of goldfish and how to tell them apart. Hopefully this will help you to see which (s)he is?

      (P.s. I removed your e-mail address from your comment to prevent you getting spammed!)

  3. Avatar
    Linda Hagen

    What a wonderful site and I’m so glad I found it! We have had Albert and Victoria (the single tail goldfish) for years now and have recently moved them up to a bigger tank. I was wondering about light as we had never used one before. They live in quite a sunny room and get lots of natural light but then come bedtime – it’s dark. I tried the light – they didn’t seem to be too impressed so I’ve put it away for now. Anyhow, just wanted to say what a great site and I have bookmarked for future reference.

    • Wendy Kathryn
      Wendy Kathryn

      Hi Linda,

      Thank you for the kind words, always nice to hear good feedback 🙂

      Regarding the light: They will still need a day night cycle, much the same as we do….but is it during the day they aren’t fond of it? Could it perhaps be too bright a bulb for the tank size? (just guessing here.)

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