How To Take Care Of A Goldfish: Ultimate Guide | Aquascape Addiction

How To Take Care Of A Goldfish: Ultimate Guide

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Want to know how to take care of a goldfish? this is the ultimate guide that covers everything you need to know and more.

How To Take Care Of A Goldfish: Ultimate Guide

Goldfish certainly are a number one choice for a beginner fish owner around the world. They are a hardy breed of fish, very resilient to most things, and generally very easy to take care of. If you are a beginner, this is probably the best type of fish to get. However, all of that being said, a goldfish is still a living creature and therefore needs to be treated appropriately.

Today we’re here to tell you literally everything there is to know about looking after goldfish. How to feed them, take care of them, what size tank to get, water conditions, breeding, and much more are all things that we are going to discuss.

We want you to be successful at goldfish keeping, and with this all-inclusive guide, you really should not have any problems at all.

a Veiltail Goldfish

Goldfish Facts

Before we dive into taking care of goldfish, let's first look at some quick facts;

  • Goldfish are scientifically known as Carassius Auratas.
  • They hail from Asia.
  • Part of the Cyprindae fish family.
  • Related to carp and koi.
  • Is a cold water fish.
  • Goldfish are great for beginners due to their resilience.
  • Goldfish require minimal care.
  • They like having tank mates.
  • They can grow up to 12 inches in length (or longer).
  • Goldfish can get very old, well over 10 years if treated well.

Here Is The Ultimate Guide On How To Take Care Of A Goldfish

We have split the guide up to cover; tank size, feeding, tank mates, filters, air pumps, food, diseases, temperature, and common mistakes. This covers everything you need to know on taking care of a goldfish!

Tank Size

Goldfish in a bowl

A very important thing when it comes to housing your goldfish is the size of the fish tank which you keep it in. Many people opt to go for the classic goldfish bowl, a small, cramped, and woefully uninspiring way to keep your goldfish.

The problem with bowls is that they are boring and don’t give your goldfish much room for exercise, not to mention that the round glass completely distorts the way which your goldfish sees the outside world.

However, that is all beside the point, because size is what really matters here, and we mean the size of the goldfish. Sure, some goldfish can stay fairly small, which does have to do with how big the tank is.

Some goldfish will stop growing once their spatial requirements are not being met anymore. That being said, many people probably do not realize that goldfish can grow up to 8 or 10 inches in length and that the goldfish they buy at stores are still small babies.

Generally speaking, a goldfish tank (for fancy goldfish) should be at least 3 feet long and 20 gallons in volume, with an additional 10 gallons of volume for each additional fish. Also, for regular goldfish, you will want a 4-foot long tank with a 30-gallon volume, with an additional 12 gallons for every extra goldfish.


Feeding your goldfish is something that we will cover in much greater detail later on in this article. However, what does need to be said is that you need to be careful not to overfeed your goldfish as that can cause serious health issues and even death. Remember to never feed your goldfish too much at once.

Small feedings several times of day is the best way to go about feeding your little goldfish. Also, remember that if you feed them too much, not only will the goldfish get sick, but they will leave excessive amounts of uneaten food floating around in the aquarium water, and that can contaminate it to the point of being uninhabitable

This post covers the best goldfish food options and further information on feeding.

Goldfish Tank Mates

Goldfish tank mates

We don’t want to start listing off a multitude of fish which you can keep in the same tank as your goldfish because the list would be fairly extensive (we have covered tank mates separately here). There are, however, some general rules that you should follow when considering some tank mates for your goldfish.

First of all, the goldfish’s tank mates need to be able to thrive in the same water conditions as the goldfish. This means similar pH levels, water hardness levels, and temperatures too, plus of course, the difference between saltwater and freshwater. You can’t house fish together when they need different types of water parameters to stay healthy, with the most important thing to keep in mind being that goldfish like fairly cold water.

Another thing to keep in mind before buying any tank mates for your goldfish is the spatial requirements of all fish. Just remember that the more fish you have, the bigger the tank needs to be. Another rule to follow is not to get any fish which are much bigger or faster than your goldfish, especially ones that may be territorial and aggressive because this is a great way to see your goldfish get eaten.

On that same note, if you get smaller fish, make sure that they are quick enough to get away from your goldfish, or that they seem unappealing as a snack at the very least, because your goldfish may indeed try to eat smaller fish which it might view as prey.

Another thing to keep in mind is that you probably should not mix various types of goldfish together. Just to give you an idea of which fish make for decent goldfish tank mates, you could try housing them together with white cloud mountain minnows or zebra danios.


Goldfish are seriously dirty fish. Well, ok, not that dirty, certainly not as dirty as something like a dog or pig, but they do produce a lot of waste. When it comes to fish, goldfish eat a whole lot of food, they produce a whole lot of waste, and they like to make a mess in the tank too. So, if you were wondering whether or not you need a filter for your goldfish tank, the answer is an absolute yes.

Without proper filtration, your goldfish tank will become polluted, cloudy, toxic, and may, in fact, kill the goldfish. You need a good filter to control ammonia, nitrite, and nitrate levels, you need one to get rid of fish waste and excess fish food, and you need it to control the growth of bacteria.

One of the most important things to remember is that a filter or a goldfish tank should be able to filter 10 times the water volume in the tank per hour at the very least. So, if you have a 20-gallon tank, the filter should be able to process 200 gallons of water per hour in order to serve as an effective filtration agent.

Now, when it comes to what kind of filter you should get for your goldfish tank, you can choose between an external filter and an internal filter. Internal filters will work just fine in terms of cleaning the water, but they do have their drawbacks.

First of all, an internal filter will take up valuable real estate in the tank, thus taking away from the room your goldfish has to swim around in. Moreover, internal filters are usually much less thorough in terms of their cleaning jobs.

The best type of filter to get is an external filter that hangs off the back of the tank. This type of filter may cost you a little more than the internal type, but they tend to work much better.

These filters tend to be bigger and have much more filtration media inside, as well as different types of filtration. When it comes to keeping your goldfish alive, the more filtration power the filter has, the better. Moreover, an external filter will also not take up space inside of the fish tank.

For more information check out this post, it covers some of the best aquarium filter options.

Air Pumps

One perception that many new fish owners have is that an air pump is absolutely necessary for any fish tank in order to keep them alive and to keep the water oxygenated. This is wrong, just wrong. Yet, an air pump will add minimal amounts of oxygen to the water, but not enough to make a big difference. Generally speaking, you really don’t need an air pump for your goldfish.

The water itself has more than enough oxygen in it, the surface area of the water is where oxygen is absorbed, and your filter will more than likely do a fine job at oxygenating the water by itself. The most important thing to keep in mind is that it is the disturbance of the water at the surface which oxygenates the water, something that every good filter will accomplish on its own.

There are some specific cases where you may want to consider getting a filter. First of all, if you have many fish in the tank breathing oxygen combined with little plant life, then there will be less oxygen in the water.

Second, if your fish tank has a small surface area with minimal air to water contact, you may want to get an air pump. Also, if the water is very still and the filter is not doing a good job at oxygenating the water, you may want to spring for an air pump.

Next, the higher the water temperature is, the lower the level of dissolved oxygen in the water will be, which is something that also may call for an air pump, but this is generally not a problem with goldfish because they live in cold waters.

If you are not sure whether or not your goldfish has enough air to breathe, some signs of a lack of oxygen include rapid gill movement, lethargy, and gasping at the surface, all being cases where you would definitely want to consider getting an air pump.

More on aquarium air pumps here.


A very important part of keeping your goldfish healthy has to do with feeding them. Now, right off the bat, the most important thing to keep in mind is that goldfish are not too big on protein. While they do need a fair amount of protein to survive, it is much less than with many other types of fish. Goldfish food should be 40 percent protein at the very most, which is why goldfish food makers produce food that is much higher in carbs than protein.

What this means is that you should not feed your goldfish too many live foods as that will be too much protein for them. Also, you should not feed them generic fish food as those foods will most likely not meet the specific dietary requirements of your goldfish. The best way to go is to buy some specialized goldfish food. This food may come in the form of pellets or flakes.

One thing to remember is that there are goldfish of different sizes, with some being too small to really eat pellets, in which case you will want to feed them goldfish flakes. You should aim preferably for food that sinks to about halfway down the tank before it is eaten.

Food that sinks to the bottom will be hard to dispose of if left uneaten and can contaminate the water. At the same time, floating food is also not ideal because goldfish will swallow air when eating it, and that can cause some serious digestion issues.

Generally speaking, goldfish will eat small insects and insect larvae, small crustaceans, and plant matter too. This means that you can always try feeding your goldfish peas with the shells removed, some boiled vegetables, bloodworms, and brine shrimp too. Remember that freeze-dried foods are better than live protein snacks because live food may harbor disease that can make your goldfish sick.

Your goldfish should not be overfed by any means because they will keep eating and eating, more or less until they pop. So, a good rule of thumb is to feed them small pinches of food 3 times per day, always making sure to not add too much at once. On an interesting side note, the colder the water is, the slower the metabolism of your goldfish will be, with the result being a decreased need for food.

Cleaning The Tank & Water Changes

One of the best ways to keep your goldfish tank clean and free of harmful toxins and pollution is to regularly change or cycle the water in the tank. How often you change the water and how much water you change will depend on factors such as how many fish you have, the amount of plants you have (if you need some safe suggestions, here is our top 10 plan suggestions), and the efficacy of your filter.

However, the general rule is that you will want to change the water in the goldfish tank once per week, and each time you do, you want to change no more than one-third of the total water volume.

Cleaning the tank itself is not all that difficult though. First, start by turning off any electrical components such as the filter or air pump. Then, take your aquarium vacuum (we have reviewed 5 good options here), with one end in a buck and the other in the tank, and use it to remove the desired amount of water, plus waste, from the tank into the bucket. Keep moving the vacuum along your substrate until the majority of the waste is gone and about one-third of the tank water has been removed.

Now it is time to take out the filter sponges. Place them inside the bucket of tank water that you just emptied and squeeze them out to remove any debris or waste. Reinstall the sponges in the filter and then place the filter back into the tank. Everything else, including rocks and decorations, should be washed the same way as you washed out the filter sponges.

Next, you want to empty the bucket of the old tank water and fill it with fresh tap water. Always remember to treat the tap water with the right bacteria and chemicals before reintroducing it into the tank. Simply pour the water back into the tank, keeping in mind to do it slowly and gently so as not to disturb the fish or severely disrupt water conditions.

Common Goldfish Diseases

There are a few different diseases and illnesses which goldfish can suffer from, some of which may be more serious than others. Let’s just talk about some of the most important ones.


Constipation in your goldfish can be due to feeding it too many carbs and too much protein. Your fish is constipated if it has a swollen belly, does not defecate much, or is floating on its side. A simple solution to the problem of a constipated goldfish is to feed it some greens as they will act as a laxative.

Ammonia Poisoning

If your fish has blackened or burned looking skin, specifically on the tips of its fins, then your goldfish most likely has ammonia poisoning. This can quickly become fatal so you will immediately want to do a water change. You should get an ammonia test kit so you can accurately keep track of ammonia levels, and you should also get a specialized fish medication to help the slimy protective coating on the goldfish regenerate.

Swim Bladder

If your goldfish has something called swim bladder, it will have a hard time staying upright and may face downwards, upwards, or be on its side. Swim Bladder is actually a genetic problem and has no cure, but the effects of it may be decreased by treating it the same way as you would a constipated goldfish.


Ich, otherwise known as Ick, is caused by a parasite and can be characterized by rapid gill movement and white spots. To get rid of ick, you need to clean your whole tank from top to bottom and also get a special treatment specifically designed for removing the parasite.

You can also try adding 3 tablespoons of salt per gallon of water to your tank. Keep in mind that while goldfish can handle low levels of salt, that is definitely not the case for all fish.

Fin Rot

Perhaps the most common disease which your goldfish may suffer from is known as fin rot. The tips of the fins of your goldfish will get cloudy, then white; then they can split apart and literally rot away, something that will end up being fatal when left untreated for a prolonged period of time.

One of the best solutions is to use a hydrogen peroxide swab and dab the affected areas of your goldfish once every 24 hours.

The salt treatment mentioned for ich may also work. If that does not work, you can always try adding medications to the water, but be careful because high doses may burn your fish. Also, if need be, you can actually go to your vet to get antibiotics injections too.

There is also situations where your goldfish will be swimming upside which we have covered separately on this post.

Temperate For Goldfish

Simply put, goldfish are cold-water fish, so the water does not need to be very warm at all. Goldfish can survive in waters that are close to freezing, but to encourage good growth the water should be at least 10 degrees Celsius. They can survive in water anywhere from around 7 degrees Celsius to 28 degrees Celsius, but in all reality, the colder, the better.

However, anything above 30 degrees Celsius will harm your fish, and any hotter than that, and they will most likely die. A good temperature for decent growth and health is around 20 degrees Celsius. As you can see, goldfish are very resilient when it comes to water temperature

Breeding Goldfish

Breeding goldfish really is not that hard. First off, there are a few things that you will need to have. You need the main fish tank, a smaller tank for the fry, a heater, some plants, a sponge filter and air pump (both for the fry tank), and a spawning mop.

A spawning mop is a tool that fish breeders use to protect the eggs from the parent goldfish, plus it makes moving the eggs and fry around much easier. Keep in mind that goldfish need to be mature, so about 1 year old, before you can sex them to determine their gender.

An important thing you have to do to get your goldfish to spawn is to raise the water temperature. This is because goldfish usually spawn in spring, which means that their cycle is triggered by changing temperatures.

Therefore, you want to raise the water temperature steadily from 10 Celsius to 20 – 23 Celsius by around 2 Celsius per day. When the goldfish are ready to mate, the men should have something that resembles pimples on their gills, as well the females should look fatter than usual.

If all goes well, the female should deposit her eggs near a planted area of the tank or in the spawning mop. Afterward the male should then fertilize the eggs.

Ok, so, goldfish will eat their own eggs so you need to remove them from the tank as soon as you can. Remove the spawning mops or the eggs (gently) and place them in the fry tank. The water temperature in the fry tank needs to be virtually the same as it was in the main tank.

While doing this, you may notice that some eggs are darker than others. The darkest ones can be disposed of if you wish because the lighter the eggs are, the higher the chances of hatching.

Once the fry hatch, don’t feed them until they start moving around and swimming, which may take a few days. Simply add some hard-boiled egg yolk into a jar of water, shake it until the water is cloudy with dissolved egg yolk, and slowly pour small amounts into the fry tank.

Where to Keep Your Goldfish

The common goldfish can technically grow to be up to 18 inches in length, and for this reason, experts recommend that you have a tank that is a minimum of 40-gallons. If you have two goldfish, then your tank should be 55-gallons.

You also don't want to put your goldfish in a fishbowl because it can get too messy and the water will have to be changed out very, very regularly. Fishbowls are also often far too small to fit any kind of filtration system, and there is rarely enough room for proper oxygen exchange for the fish.

When choosing an area in the home to keep your tank, you need to consider a few things. Watch for air conditioners or heaters in the area and don't place your aquarium in any area of the home that will experience temperature changes.

You also want to keep the aquarium away from the windows because ambient light can encourage algae growth and windows are often drafty. If you have to place the aquarium where there is any sun, be sure to use a shade to protect the tank from the ambient light.

Finally, if you have small children and pets, you definitely want to choose a place that is out of their reach.

Common Mistakes Made By Goldfish Owners

There are a few common mistakes that many first time goldfish owners make, many of which we have touched on above. Let’s just quickly talk about the biggest ones.

  1. Buying a tank that is too small, or even worse, buying a bowl. These things can be over a foot long so they need their space.

  2. Putting too many goldfish in the tank is another big mistake many people make. Keep in mind the spatial requirements of goldfish which we talked about above. One goldfish needs at least 20 gallons of water and an extra 10 for every additional fish.

  3. Many goldfish owners do not cycle their tanks, cycling which is necessary for getting rid of ammonia and other substances in the water. This means having to add good bacteria to the water.

  4. Do not over feed them. Keep in mind our advice on feeding which we provided above. Too much food can result in illness and the death of your goldfish. Also, never buy poor quality fish food.

  5. Messing around with water changes is another mistake that many people make. Never change more than 1/3 of the water at once. That being said, the water should be changed at least once per week. Also make sure to never use untreated tap water.

  6. Don’t clean the filter, rocks, or gravel with tap water because you will wash away the good bacteria, a mistake that many first time owners make.

  7. Another mistake that many make is to not quarantine a new fish. Always keep a new fish in a separate tank for 2 weeks before adding them to the main tank.

Moon Jellyfish are cool pets to consider too, we have covered a separate guide on them here.

Goldfish FAQ

How can I tell if my goldfish is sick?

If your goldfish is sick, you will most likely find that their fins are clamped close to their body.

Other signs include frequent jerky swimming motions, no response at feeding time, the loss of color, swimming listlessly, and long periods of time laying in the bottom of the tank.

How many goldfish types are there?

There are over 100 varieties of goldfish and more are appearing each year.

How can you tell if the goldfish is male or female?

In order to determine sex, the goldfish needs to be at least a year old and in excellent health. The other conditions in the aquarium also need to be ideal in order for the fish to display characteristics of the different sexes.

When viewed from up above, a female goldfish will appear much rounder than males. However, males can still have very plump bodies, so this sign is easier to distinguish with the slim single-tailed goldfish.

Which goldfish are the best for beginners?

Comets, Shubunkins, and Fantails are the best goldfish for beginners. You should also remember to keep the single-tailed goldfish away from the Fantails because the Fantails will almost always reach the food first.

Can I use oxygenating weeds over a filter?

Filters are always recommended for goldfish because the aquatic plants will oxygenate the aquarium water during the day but not at night. Goldfish are also omnivores, so they like the taste of the live plants and will most likely eat them.

How do I clean the gravel?

The gravel in the bottom of the aquarium is filled with a ton of good bacteria, and if you take it out to rinse it, then you are washing away and destroying the good bacteria. Instead of removing it, you can use a gravel cleaning siphon.

Do goldfish need a light?

You do not need to provide your goldfish with a light. However, if you want the tank to be more aesthetic, then you can choose one with lighting. It should only be on for 8 hours per day, or you will find that the glass of your aquarium will quickly develop algae.

What is the life expectancy of goldfish?

Some goldfish, when properly cared for can live for over ten years with others living for several decades. However, with improper care and neglect, they will not survive long, and their life will definitely be cut much shorter.


There you have it, absolutely everything there is to know about goldfish. With all of this information, you should have no problem at all in regard to keeping your goldfish alive and healthy!