Goldfish
Welcome to the wonderful world of goldfish! These magnificent fish can trace their origins back over 1,000 years to ancient China, where they were bred for their striking colours and elegant fins. Nowadays goldfish remain a popular and relatively undemanding choice as a first pet, although it’s worth remembering they are still a species of carp and can reach sizes in excess of 25cm. Provided their needs are met in terms of an appropriate aquarium, reliable filtration system and a nutritious diet, goldfish can be charming companions for 20 years or more.
What next?
View the information below to learn the essentials for owning a pet goldfish.
Take the test, and when you have passed, you will receive a certificate to show to your pet shop and prove your knowledge.
Information for owning a pet goldfish
The Pet Know How tests are designed to test your basic knowledge of keeping a pet of your choice. They will help you understand the needs of the animal and some of the important things you need to consider if you were to have one as a pet. Once you complete a test you won’t be an expert keeper but you will be in a better position to make an informed decision and decide if you are able, and willing, to take on the responsibility.
In this section, you will find a wealth of knowledge compiled by pet experts to provide you with the valuable information you need regarding owning a pet goldfish.
Work your way through all the sections, and when you feel ready, register yourself to take the test and earn a certificate that proves your goldfish knowledge.
Introduction
Goldfish are perhaps the most widely recognised aquarium and pond fish and have been kept for many centuries. They were first kept in bowls in China in the third century and imported into Europe in the 1700s. Goldfish can be found in many shapes and colour variations, including the sarasa comet and shubunkin, and many colours, including red, blue, yellow, black, white and orange.
Biology
Carassius auratus is the scientific name for the Goldfish which is a relative of the carp. They are members of the Cyprinidae family. Goldfish have reportedly grown to sizes of 40cm+, although in an aquarium, a maximum size of up to 25cm is more common. Goldfish can live for many years in an aquarium with good water quality. There are many reports of fish living 6-8 years and even up to 20 years or more. Goldfish can be sexed during the breeding season in the spring and summer. Males develop tubercles (white spots) on their gill covers and pectoral fins. Females have deeper bodies compared to males.
A healthy goldfish should.....
Have clear bright eyes
Have undamaged fins
Have intact scales
Have no ulcerations or bumps
Have appropriate swimming behaviour
Have steady breathing
Do not purchase a seemingly healthy fish if sickly fish are present in the tank with it. Signs of disease can include clamped fins, flicking against gravel or décor and shimmying (wobbling). Diseases can be easily carried by fish that do not show any clinical signs. If in doubt, ask your OATA retailer for advice as they will have in-depth knowledge and experience.
Water requirements
Goldfish are an adaptable species and can tolerate a wide range of environmental conditions. It is suggested that you maintain the water quality within the following guideline values:
Temperature: between 4-25°C
pH: 6.0-8.0
Ammonia: Zero mg per litre
Nitrite: Zero mg per litre
Nitrate: Not to exceed 20 mg per litre above normal tap water levels
Hardness: Moderately soft-moderately hard (5-19°dH)
Aquarium requirements
As a general rule you should, within reason, buy an aquarium as big as possible. Ideally, it should be able to accommodate your goldfish once they are fully grown (they can grow up to sizes of 25 cm in aquaria). An adult goldfish should be kept in at least a 100 litre aquarium, allowing for an extra 50 litres per additional adult fish, otherwise, you must be prepared to buy and upgrade their aquarium as they grow. If your goldfish is a non-fancy variety, you can transfer them to an outdoor ornamental pond. The larger the aquarium, the more stable the environmental conditions such as temperature and water quality will be. Whatever the size, a filter is always essential.
Aquarium requirements continued
The tank should also have gravel and ideally live plants present. Goldfish can readily eat live plants so do ask your OATA retailer for advice on which plants are suitable for goldfish. If live plants are not used, then the addition of plastic plants and suitable ornaments is recommended, such as plant pots or model caves, which supplies the fish with shelter.
A heater is not required for goldfish unless they are kept in a very cold room. Although goldfish are coldwater fish, they do not tolerate extreme fluctuations in their water temperature which can cause stress and lead to disease. Thus, their aquarium should not be situated near any draughts or heat sources. It should also be out of direct sunlight and away from loud noises, vibrations and sudden movements. Over tank lighting is recommended to maintain correct day-night cycle.
Checking your aquarium
Before adding any fish, seek advice from your OATA retailer to make sure that your aquarium is an appropriate size for the number of Goldfish you would like to keep. Check that the water quality in your aquarium is suitable i.e. levels of ammonia and nitrite are zero. Only increase the number of fish you have in your aquarium slowly as the population of beneficial bacteria established when maturing your aquarium filter need to increase every time more fish are added and feeding increases. Overstocking or stocking your aquarium too quickly can result in ‘new tank syndrome’. This occurs when there are not enough nitrifying bacteria to cope with the increased waste load, leading to unhealthy levels of ammonia and nitrite and often fish may die.
Introducing your fish
Your OATA retailer will usually sell your fish to you in a plastic bag. Try not to keep them in this for too long. Once purchased, take your new fish home as quickly as possible as fish are easily stressed by bright lights, extreme temperatures, noise and movement.
Once home, your fish will need to acclimatise to their new environment and a common method of doing this is known as the ‘floating bag’ method. Switch off the aquarium lights and take the bag containing your new fish out of its outer wrappings carefully, avoiding exposure to bright light. Float the bag in the water of your tank to ensure the temperature in the bag is the same as the aquarium water. After 10 minutes, slowly introduce small amounts of aquarium water into the bag containing the fish for up to 20 minutes. Once complete, carefully release the fish into the aquarium whilst introducing as little bag water into the aquarium as possible. After this, dispose of the bag and any excess water appropriately. Monitor your new fish carefully for the first week, paying particular attention to water quality. If in doubt, contact your OATA retailer for advice.
Maintenance
Maintain the water in the aquarium within the accepted parameters highlighted in this guide. You may need to do regular water changes to achieve this.
Always buy test kits and regularly check the water for ammonia, nitrite, nitrate and pH. This will allow you to make sure the water in your aquarium is not causing welfare problems for your goldfish. Establish a routine for testing the water in your aquarium. Record your results to enable you to identify fluctuations quickly and also check the temperature of the water.
Never siphon by mouth a fish tank can harbour bacteria which can be harmful if swallowed. Buy a specially designed aquarium gravel cleaner which can be started or primed without the need to place the siphon in your mouth. Always wash your hands making sure to rinse off all soap residues, before putting them into your aquarium, or use long sleeved rubber gloves. Wash your hands again afterwards and certainly before eating, drinking or smoking.
Maintenance continued
Water testing kits are essential as goldfish can be very dirty, which can increase levels of ammonia and nitrite. Water should be checked on a regular basis (once a week) to ensure it does not slip below the standards given in this guide.
At least once every week, a partial water change of 25% is strongly recommended (a siphon device is useful to remove waste from the gravel). The water should be tested regularly (at least once per week) to ensure that ammonia and nitrites don’t build up. Ensure that the replacement water is treated with tap water conditioner to remove any harmful chlorine or chloramine present before adding to the aquarium.
Filters should be checked for blockages. If the filter needs cleaning, then do not run it under the tap because any chlorine or chloramine present may kill the beneficial bacterial population that has established in the media. Instead, it should be rinsed lightly in the tank water which is removed during a partial water change as this reduces the amount of bacteria which are lost.
Good husbandry is essential as goldfish can be stressed by even the smallest amounts of ammonia and nitrite which may then cause them to develop various diseases. Test the water to monitor the ammonia, nitrite and nitrate levels, together with pH and water hardness every week, especially during initial set-up and after adding extra fish.
What to watch out for
All fish will have slight variations in their behaviour or appearance, but keeping an eye on any changes in the following will help to identify any potential problems before they become a real health issue:
Swimming behaviour – hanging at the surface, sitting on the bottom or erratic swimming
Colour – turning a darker or paler colour than normal
Temperament – changes in level of aggression or hiding more than normal
Breathing – gill covers moving at a slower or faster rate than normal
Appearance – development of white spots or fluffy growths, loss of fins or scales
Condition – increase or decrease in body weight and condition
Feeding – reduced intake or lack of interest in food
If you are concerned about the health of any of your livestock, then test your water quality and contact your OATA retailer for further guidance.
Feeding
Goldfish are opportunistic feeders in the wild and will take most food types. In the home aquarium, they should be fed with a good quality flake or pellet. They are insatiable feeders and will constantly look for food. Try not to over-feed them as this can lead to a build-up of uneaten food which breaks down releasing toxic waste into the water.
Goldfish should only be fed what they can eat within a few minutes, once a day. Take care not to overfeed as this can lead to a build-up of uneaten food which breaks down releasing toxic waste into the water. If in doubt ask, your OATA retailer for advice on appropriate feeding levels.
Compatibility
Goldfish can be kept by themselves or with others. It is not advised that comet goldfish are kept with fancy goldfish because comets swim faster than the fancies and they often out-compete them for food. In some cases, there are reports of boisterous goldfish fin-nipping the slower swimming fancy varieties.
Breeding
Goldfish can be successfully bred in large home aquariums. It is more likely to occur if males and females are kept in a ratio of 2:1 (males: females). Spawning can be induced by slowly raising the temperature (in effect, mimicking what happens in spring) to approximately 20°C. It often occurs following a partial water change.
Males will chase the females in a courtship display. The fish will lay eggs in plants or a spawning mop which should be removed afterwards as goldfish are notorious for eating their eggs and fry. If successful breeding has taken place, then the eggs will hatch within three days and dark-coloured fry should be seen swimming within a few days.
Before purchasing your goldfish
Before purchasing your pet goldfish make sure:
You have the appropriate equipment and position for the aquarium
You have researched all the species in which you are interested and your final choices are all compatible
You are familiar with how to transport and release your fish
You are aware of the daily, weekly and monthly maintenance your aquarium will require
You are prepared to look after your fish properly for the duration of their life
The aquarium is of a suitable size that ideally can accommodate the fish once they are fully grown
Water parameters are as advised in this guide
Aquarium is cycled and ready to receive fish
Shopping list
Owning a pet is a financial as well as a moral responsibility. In order to properly care for a goldfish the following items are essential and you should ensure that you are ready to commit to both the one-off and ongoing costs involved with having a pet.
Water testing kits (ideally ammonia, nitrite, nitrate, pH and water hardness)
Gravel cleaner/siphon cleaning device (recommended)
Aquarium decorations and/or live plants
Bucket for water changes
Glass or acrylic aquarium
Filter
Heater
Lighting (required for live plants)
Gravel or sand
Tap water conditioner/dechlorinator
Pet code of practice
Owning a pet is a responsibility and owners must always ensure that they act in a way that ensures the best welfare for their pet and does not endanger the local ecosystem. Pet’s (companion animals) must never be released into the wild. It is illegal and for most species this will lead to an untimely and possibly lingering death, as they are not native to this country. Any animals or plants that do survive might become harmful to the environment. If you can no longer keep your pet then seek advice at a local pet store, rescue centre or specialist pet club.
Soiled substrate, cage décor and waste water, particularly from fish tanks or amphibian housing, should also be carefully disposed of or treated so that potentially harmful diseases or live food can’t escape into the wild.
Are you ready?
Now that you have made your way through the presentation, it’s time to take the test and move one step closer to proving your knowledge and receiving your certificate.
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