Last Updated 07-22-2023 by Grant Lord.
In the past Goldfish were considered to be small, short-lived aquarium fish that were very hardy and could be kept in small glass or plastic bowls.
Today, we know Goldfish are long-living, large-growing aquarium fish that thrive when given the right living environment.
Providing the right indoor environment requires a Goldfish tank that suits the number and variety of Goldfish you plan to keep and how much maintenance that will require.
Before we discuss tanks, let’s first discuss why bowls are not suitable for Goldfish
Goldfish bowls were used to keep Goldfish in for many years.
There were advantages to using a Goldfish bowl:
Disadvantages of bowls are:
It is possible to keep small Goldfish in a bowl (it is now banned in some more enlightened countries), but, because of the increased maintenance required and its harmful effects on the lifespan of Goldfish, bowls are now considered the worst environment to keep a Goldfish in.
Before rushing out and buying a tank that may be unsuitable, first, ask yourself the following questions:
What Goldfish variety or varieties do I plan to keep? Some Goldfish varieties grow large, 8-12 inches in body length, and these are also the cheapest and most commonly kept varieties.
What size aquarium do I need? This raises the following questions:
How will I make water changes? Can the aquarium be siphoned and filled using a hose; using buckets is too time consuming for a large aquarium?
Will I be able to maintain the tank easily? Tall tanks can be hard to reach down to the bottom unless special equipment is used.
Where is the aquarium going to be placed? Aquariums should not be placed near windows or any source of direct or strong lighting, unless you plan to run a UV clarifier.
Is there a nearby power supply for the filter?
The simple answer is:
I go into more detail about tank size and how much room Goldfish need here, but rarely are fully grown Goldfish available for sale.
Most fish available at pet stores are juvenile fish a few months old and between 1-2 inches (25-50mm) in length.
Before we start discussing fish sizes and tank requirements, for clarity this website only uses body length when discussing fish sizes. The reason for this is that any other measurement can be misleading.
As an example, say a Comet has a length of 6” (150mm) including its tail which can be the same length as the body. This means the Comet’s body length is 3” (75mm).
If we now use the same 6” (150mm) measurement for a Common Goldfish, its body length will be over 4” (100mm). This difference in body length means the Common Goldfish will be double the body weight of the Comet.
There is nothing wrong with starting small, but you are now aware that your fish will grow, and at some point, you will either need a larger tank, or reduce fish numbers.
I would recommend as a minimum size a 15-20 gallon 2 foot tank, 15-18 inches high and 12 inches front to back with 2 small Goldfish. I would suggest against keeping any other fish species in with your Goldfish because some a tail nippers, and as your Goldfish grow, some smaller species such as White Cloud Mountain Minnows could become food. They also add to the bio-load that the filter has to deal with.
As the fish grow, you will need to make more frequent water changes to keep the water quality high. This will be indicated by your water test kit showing the nitrate level reaching 30 ppm (parts per million) more quickly.
This is the downside of having high numbers of fish per gallon; it means you need to do water changes much more frequently.
There are two types of materials used for aquarium manufacture these days, glass and acrylic.
Glass aquariums have the following advantages:
Some disadvantages of glass aquariums are:
Acrylic aquariums have the following advantages:
Some disadvantages of acrylic aquariums are:
Aquariums come in every size and shape. You need to choose the one that is going to be best suited for its intended use, such as:
For each of these uses there is a Goldfish aquarium that suits the purpose best. For example:
When purchasing Goldfish aquariums, there are a few options available. You can:
Few sellers of aquariums include gravel, plants or filter media (the filtering material you put inside the filter) with their packages.
For aquariums that will not be used for display purposes I would suggest purchasing bare aquariums. You can then purchase only the accessories you need.
Make sure the aquarium comes with a glass two piece cover. One piece of the cover should be no wider than 3” (75mm) so it can be raised separately for feeding and netting fish without having to take the whole cover off.
The cover stops evaporation, heat loss, fish jumping out and objects being dropped into the aquarium.
If this is your first Goldfish tank, here is a check list of everything you need to set up and maintain the aquarium. Even if you purchase a complete aquarium package, make sure you are aware of what is not included.
Complete aquarium packages can be quite expensive. Before buying new, check if any second hand items are available locally.
Be careful of cheaper aquarium packages as the imitation wood such as MDF used for the stands can be easily damaged if it gets wet, as it causes the material to swell.
Once you have purchased your Goldfish tank and equipment, and possibly fish, you will want to set it up, add water, add the fish and start enjoying it.
Sometimes, with luck, there will be no problems and your fish will live long and healthy lives.
What usually happens is either the fish get sick or they die suddenly within 2-4 weeks.
There are three possible reasons for this:
Ammonia is toxic to all fish species, even in very small quantities of parts per million (ppm).
The primary function of the filter you installed is to remove ammonia, not keep the water clean.
An ammonia spike happens because the filter has not had enough time to go through the nitrogen cycle.
The nitrogen cycle is when the ammonia the fish produce from breathing and from their waste decomposing is processed by bacteria in the filter into nitrite. Nitrite is as toxic to fish as ammonia. Bacteria in the filter then convert the nitrite into nitrates, the much less harmful chemical.
You need a water test kit so you know at what stage your filter is in the nitrogen cycle, and when to make water changes when ammonia or nitrite is detected, and nitrates rise above 30 ppm.
My suggestion is don’t set up your aquarium with plants and substrate, but use it as a bare quarantine tank for 3-4 weeks while monitoring your water condition, and when nitrates are detected, you know your filter is cycled.