How to Look After a Goldfish

how-to-look-after-goldfishLooking after a goldfish properly is no easy task. Much of the commonly-held advice about caring for goldfish is painfully wrong and has led to numerous goldfish over the years passing away much sooner than necessary.

Fortunately once you understand a few simple rules you’ll find that looking after goldfish successfully can be both simple and rewarding.

Prepare for a crash course on how to look after goldfish the right way…

Selecting a Goldfish

Let’s start from the beginning and assume that you’re just considering purchasing your very first goldfish. However if you’ve recently inherited some goldfish from a friend, or suddenly found your children have won one from a fair then please feel free to move on to the next section.

For those of you learning how to look after goldfish for the very first time then you can set yourself up for success by choosing the right fish to begin with.

It’s a sad fact of life that goldfish, like all fish, tend to be quite sensitive animals. The stress of being transported to the aquarium shop combined with potential over-crowding can result in some shop-bought fish being less than healthy. Start off with sickly fish and you’ll immediately put your fish keeping exercise at a disadvantage.

But how do you identify a healthy fish?

Signs of a Healthy Goldfish

There are a number of signs that can help to indicate that a potential pet goldfish is in good health. Here are some factors to consider:

“Smooth” Appearance – You’ve probably seen a sick bird in your life; they often “fluff” themselves up and sit motionless in the corner. Likewise, many sick goldfish may be seen to have their scales protruding slightly, giving them a rather “spikey” appearance. A healthy goldfish should be sleek and smooth to the eye.

Swimming Freely – Just as with our bird analogy, a healthy goldfish will be swimming freely around the tank. Any signs of a fish that won’t swim, or that seems to be struggling to do so (such as swimming at an angle) could be symptoms of serious health issues.

No Missing Scales – While many goldfish live perfectly healthy lives after losing a few scales, the reality is that lost scales can allow infections into the body. It is not unusual to find fish with damaged scales suffering from fungal infections which have gained traction thanks to this damage.

No Distensions – There are two common problems frequently seen among pet goldfish; these are goldfish with digestive problems or swim bladder problems. Both can result in a goldfish which doesn’t conform to the usual stream-lined appearance enjoyed by most fish. Any such lumps or swellings could be cause for concern.

Reputable Seller – One of the most important factors of all, it is wise to buy only fish from a reputable supplier. Under such circumstances the fish will likely have received the proper care while they have been in the store awaiting you.

Assuming the fish you are considering meets the above guidelines then you can successfully rule out many of the potential health issues that a goldfish can suffer from.

As a final note about selecting a fish, note that goldfish with the classic shape tend to be rather more hardy than the so-called “fancy goldfish” with their rotund shapes and luxurious fins. While many children immediately fall for these “cute” looking fish, if these are your first goldfish you’d be well advised to only go for standard goldfish to begin with.

Stocking Densities

Goldfish may be kept alone or together with others. The decision really is up to you whether you opt for a single fish or bring home a number. That said, if you opt for the latter then there are two considerations you should bear in mind:

Oxygen Supplies

One of the major limiting factors in how many goldfish may be kept in a bowl or aquarium is the amount of oxygen available. Over-crowded fish can suffer from stress and may also suffer from a lack of oxygen. As a good rule of thumb aim for 20 gallons of water per goldfish.

Water Fouling

The other factor to consider is the “holding capacity” of a tank. As you might imagine, fish defecate in their water, so a tank can only hold so many fish before the water starts to become fouled. In general, therefore, fewer fish is likely to be better than more.

Goldfish Equipment

So you’ve got your goldfish – now how do you actually go about looking after them?

Let’s start off by talking about the basic equipment you’re going to need, and what to do with it.

Goldfish Bowls Vs Tanks

First and foremost when keeping goldfish you’ll need some kind of container to keep them in. Typically this decision comes down to choosing between a goldfish bowl and an aquarium. Here are some points to help you make an informed decisions about which option might be best for you:

Strengths & Weaknesses of Goldfish Bowls

Most people think that goldfish bowls are the perfect home for goldfish. Typically goldfish bowls look great, they’re cheap to buy and – well – they’re just what goldfish are meant to live in, aren’t they?

Well, not necessarily as it turns out. You see goldfish bowls also have a distinct number of disadvantages. Firstly they provide very little space to swim around in, especially if you opt to keep a number of goldfish together. Secondly, thanks to their curved shape it can actually be more difficult to keep a bowl clean than an aquarium.

Finally fitting any kind of equipment into a goldfish bowl can be problematic due to the lack of internal space.

As should be clear, goldfish bowls generally aren’t the best source of housing for your fish.

Strengths & Weaknesses of Aquariums

Aquariums might prove to be rather more expensive than goldfish bowls but they do offer a distinct number of advantages. Firstly, they provide far more room for your fish to swim around, as well as a larger surface area of water into which oxygen can diffuse.

Additionally purpose-built aquariums are generally easier to clean and fit tank equipment much better. As a final benefit of using aquariums over goldfish bowls they typically benefit from a close-fitting lid – ideal for keeping wandering hands, other pets and unpleasant chemicals out of your goldfishes’ water.

In short, most serious fish keepers agree that using an aquarium is infinitely preferable to an old-fashioned goldfish bowl.

Water Preparation

So you’ve selected your aquarium. The next thing you’ll need to do is to prepare the water for your fish. The reality is that tap water contains a range of chemicals which, whilst harmless to humans, can be problematic for your pet fish.

Putting your fish into water straight from the tap therefore poses two distinct risks; firstly the water can cause stress if it is too cold, and secondly it will contain chemicals that can harm your fish.

There are three possible solutions to this situation:

Water Treatment Fluid

The first option is to purchase a bottle of water conditioner. While such a product may seem expensive initially, just a few drops goes a long way to eliminate the potentially-harmful chlorine from the water. Due to the fact that this water can be used soon afterward (as soon as it has reached room temperature) this is normally the preferable strategy.


The second option is to collect and use rainwater. Rainwater typically lacks the chlorine found in tap water, but it *can* contain other nasty chemicals. As a result most goldfish keepers don’t utilize this option.

Older Water

A final option is to collect water from the tap at home but then to let it sit in an open container for 48 hours, at which point most of the chlorine will have disippated. It can then be safely used for your fish, though as this method requires considerable forward-planning most people just opt to use a water conditioning solution from their local pet shop.

Goldfish Filters

Goldfish can be messy animals, quickly fouling their water with faeces and uneaten food. A proper aquarium filter will help to eliminate much of this debris, keeping your aquarium cleaner and more hygienic for your pets.

This is another reason why so many people struggle to keep goldfish alive in a bowl; quite simply the water isn’t being constantly cleaned and filtered to keep it fresh.

There are a range of filters that might be used (discussed here) however whatever option you select it is best practice to utilize an aquarium filter if at all possible to help keep your fish in the best of health.

Feeding Your Goldfish

Feeding goldfish is a relatively simple process if you bear in mind one crucial element. Not only is it possible for goldfish to stuff themselves silly and end up with digestive problems but furthermore any uneaten food which sinks to the bottom of the bowl or aquarium can quickly start to foul the water. The key, therefore, is little and often.

In terms of what to feed there are a number of reliable and low-cost commercial goldfish flakes available, which represent an ideal base diet for your fish.

In addition to this it can be wise to supplement their diet on a weekly basis in order to give a more balanced diet and to add environmental interest for your fish. A range of alternatives to fish flakes may be found here.

Routine Tank Maintenance

As with any other pet, successfully keeping goldfish isn’t just a one-off affair. While the majority of your effort will be required in the early days to get your goldfish set-up working properly, there are a number of ongoing maintenance issues that you should be prepared for.

Tank Cleaning Equipment

Firstly you’ll want to regularly clean the tank. While we have full information on the subject here as a basic introduction you should expect to purchase a glass cleaner in order to remove algae or dirt from the inside of the glass. In addition an aquarium gravel cleaner can come in handy for removing sunken particulate matter from the aquarium gravel.

Lastly it may be necessary from time to time to remove objects such as rocks in order to give them a thorough scrub so buying a few decent scrubbing brushes and a bucket to assist with this routine cleaning can be helpful.

Partial Water Changes

Once you’ve got the basic equipment for keeping the internal aspects of your goldfish aquarium clean and hygienic the second aspect of routine maintenance is changing the tank water. This is hardly surprising when you consider that over time uneaten food may foul the water, as will faeces from your fish.

Over time these pollutants will progressively make the water less pleasant for your fish. If left altogether this water can slowly poison your fish, leading to fatalities. Regular water changes should therefore be considered an integral part of how to look after goldfish.

Arguably the most effective strategy is to change 15-20% of the water on a weekly basis. This water should be tipped away – such as down the toilet or onto the garden. In its place, fresh water which has been allowed to reach room temperature and which has been treated for chlorine can be used to top the tank back up.