JSPCA FISH FACT SHEET

History

Goldfish were first bred over 1500 years ago in Ancient China from brown carp.  The Chinese fish breeders noticed that sometimes these brown carp produced offspring with shiny red scales.  Through selective breeding the Chinese were gradually able to increase the extent of this reddish coloration, and so began the evolution of the goldfish.   

There are many different species of fish (more than 20,000) and a variety of different types of goldfish, but the common goldfish, Carassius auratus, remains the most popular of all goldfish.  Fish hobbyists also now commonly keep koi, Cyprinus carpio.  The common goldfish is easy to care for and can grow to 15cm (6 inches) or more.  Goldfish are naturally hardy and healthy and if kept in the right conditions, can live for up to 25 years. 

Diet

Feeding ornamental/aquarium fish: Ornamental fish are generally fed on commercial complete diets, which are usually pellets or flakes.  There are specialist foods available for specialist varieties of fish.  The food that you offer should correspond to your fishes’ natural feeding habits.  For example, fish that feed near the surface are usually given flake food, which floats readily, while bottom-dwelling catfish are typically fed on pellets, which sink to the floor of the aquarium.  Fish should be fed twice daily, but with no more than they will eat immediately; there should be no uneaten food left after a few minutes of feeding.   NEVER OVER FEED and remove any uneaten food.  This minimises the problems of water pollution.   Provide some variation in your fishes’ diet.  Supplement commercial foods with items such as bloodworms (which can be bought freeze dried).  Live foods can be fed, but it is safer to feed live foods in a freeze-dried state so as not to risk introducing disease into the aquarium.  

Feeding pond fish:  The appetites of pond fish will fall as the pond water temperature declines in winter.  Therefore, prior to the onset of winter, a change to easily digestible foods is recommended, and then again in the spring, as the fish start to eat again after their winter fast, until the water warms up.  Over the winter period itself, the fish are unlikely to feed regularly, and offering concentrated food at this stage can be harmful.  A sudden cold spell may result in the food remaining in the fishes gut for much longer than normal, where it could start to putrefy with possible fatal consequences.

Husbandry 

When keeping fish, it is essential to maintain water quality.  The main aim in water quality maintenance, and hence the use of filters in aquariums, is to control ammonia and nitrite, the main toxic products of the fish’s metabolism.   A water filter is used to remove waste water which would otherwise collect at the bottom of the aquarium and it helps to keep the water pure and clean.   There are two basic types of filtration: mechanical filtration, where the water is passed through a layer of nylon floss which traps the waste matter for you to wash out at regular intervals; and biological filtration.  Biological filters consist of a perforated plate that covers most or the entire base of the aquarium, placed beneath the gravel and attached to an airlift at one corner.  Water is drawn down through the gravel, where the dirt and waste matter are trapped and broken down by beneficial bacteria in the gravel.  The filter should be washed every two to three weeks.

Regardless of the type of filtration used, the fish will benefit from a regular partial water change.  About twenty percent of the aquarium water should be siphoned off and replaced every two weeks.  You will need to pre-treat the new water with a conditioner (available from aquatic stores) to remove chlorine or similar substances harmful to fish.  The new water should also be the same temperature as the water in the aquarium before pouring it into the tank.

In light, aquatic plants convert carbon dioxide produced by the fish to oxygen; they also use the nitrate, produced by the breakdown of the fishes’ waste, as a fertilizer.  An aquarium that has few or no living plants is therefore far more likely to have a problem with the growth of algae.  

However, excessive light exposure can result in heavy algal growth, so avoid placing your aquarium in front of a window.  Also, the water could become too hot in aquariums in front of sunny windows, which could have disastrous, even fatal, effects for the fish.

Always wash new plants before placing the in your aquarium, so that you avoid introducing any diseases or parasites which could harm your fish.  Proper lighting conditions will be essential for plants to thrive.  Alternatively, plastic plants are available for use in aquaria. 

Regular maintenance of the aquarium is necessary.  

Before purchasing any fish, check that they appear healthy and remember to consider the length of the fish when adults, if purchased as young stock, so that you not do inadvertently overstock.  Quarantine new purchases for six weeks in a special tank before putting them with other fish.  Keep a net and other aids for the use in the quarantine tank only.  

Once the fish have been transported to your aquarium, float the bag unopened in the aquarium for about 20 minutes to allow the water in the bag to adjust to the temperature of the aquarium water.  Once the water temperatures have equalised, catch and transfer the fish individually, using a special net, and dispose of the bag water.  If you simply tip the water from the bag into the aquarium, there is a risk that you could introduce potentially harmful microbes into the aquarium from the bag water. Avoid handling fish directly because you may damage the mucus covering their bodies.

Cold water, freshwater fish – for example, goldfish

Goldfish can be kept indoors in a rectangular tank or aquarium, without a heater, of a minimum size of 45 x 30 x 30cm (for four goldfish).  It is important to choose a large aquarium at the beginning, so there will be space for the goldfish as they grow.  Goldfish do not need heated water; any sudden changes in temperature can be fatal.  A ventilated lid on the tank helps to prevent evaporation and stop fish from jumping out and any predators, such as cats, jumping in!  The bottom should be covered with clean gravel. Wash the gravel thoroughly before putting it into the tank, otherwise it will create a scum on the water’s surface.  The tank must be placed on a strong, level base, away from noise, bright lights or draughts.  Large stones can be provided to make artificial ‘caves’ and only select hardy cold-water plants such as Canadian pondweed for a goldfish aquarium. Plants are useful to offer hiding places in the tank.

Water quality is very important for fish health, so a power filter is useful to help keep the water clean and an air pump, of a suitable size for the aquarium, is also advisable, especially if the tank is kept in a warm room, in order to ensure good aeration of the water.  

Warm water, (tropical) freshwater fish - for example, tetras

An aquarium of size 60cm long by 38cm high and 30cm wide may accommodate about 20 fish, measuring an average of approximately 3-4cm each.   Tropical freshwater fish can be set up in a similar way to that recommended for goldfish, with a filter.  In addition, most tropical fish will require a temperature of 23-26C, which should be maintained by using a thermostatically controlled heater purposely designed for aquariums.  Most heaters incorporate a thermostat; these are often called ‘heaterstats’. You will need a thermometer to check that the heater and the thermostat are functioning properly (a digital thermometer is usually attached to the outside of the tank for this purpose).

A power filter to assist with circulation of water in the tank is also recommended. Water quality as well as temperature, is very important for tropical fish health.  An air pump to increase aeration to the tank is also needed. 

Lights will need to be fitted over the aquarium, which means that a special hood or separate cover needs to be purchased.  Lighting is also needed for the aquarium plants to grow. For tropical freshwater fish, fluorescent lighting, of adequate wattage for the size of the aquarium, should be switched on for approximately 12 hours per day.  

Care in a pond

Setting up an outdoor pond, especially for koi, can be costly and time consuming.  Careful thought must be given in the design of a pond, for example, ponds overhung by trees are likely to become polluted by leaves falling into the pond water.

Koi, especially, are often destructive towards vegetation, hence these fish are usually kept in clear water; a pond filter that is of the appropriate turnover relative to the volume of the pond will be essential for these ponds.  In the case of goldfish, oxygenator plants such as Canadian pondweed can be included.  Fountains can also benefit the fish by improving the oxygenation of the water.

Common Diseases and Ailments

Constipation – this can be indicated by a long strand of trailing faeces, like a length of cotton thread coming from the underside of the fish. It may be related to the feeding of dry food only.  By offering a more varied diet, including live foods in a suitable form for the type of fish, it may help to resolve the problem.  The addition of fresh green food to the diet of vegetarian species may also help.

Ulcers - ulcers may be secondary to septicaemia or to wounds (damage from parasites or physical trauma) that become infected.

Dropsy – this is only a symptom and there is a range of causes.  It is often seen in goldfish, with infected individuals suffering from swollen abdomens which cause them to have difficulty in swimming   Not all cases seem to have infectious origins, but affected fish lose their appetites and, in the case of infectious dropsy, death will follow rapidly.  

Swim-bladder disorder – bony fish have in their bodies a sac of air called a swim bladder.  By filling the sac with air, or emptying it, they can float at different levels in the water.  (Boneless fish, such as sharks and rays, do not have swim bladders, so must keep swimming to stay afloat.)  If a fish seems to be experiencing difficulty in swimming, it may be suffering from an incurable swim-bladder disorder. Fancy goldfish are particularly vulnerable to this condition, which causes them to lose their buoyancy.  In the case of tropical fish, swim bladder disorder is often linked with old age.

Sudden death – a most worrying situation when most, if not all, of the tank occupants are suddenly found dead.  This may be due to environmental reasons, rather than an outbreak of illness.  Check the water.  In any event, immediately change up to one quarter of the volume of water to stabilize the condition of any remaining fish.  Check the functioning of the tank equipment, as it could be that the filtration system has failed.  For tropical fish, check the heaterstat is working. If the thermostat is not working, the heater may have continued to warm the water.  Check the thermometer.  A drop in the water temperature, perhaps by a power cut, is far less severe than a rise in water temperature.  In the event of a power cut, once the power is switched back on, the water temperature will gradually rise again. 

Poisoning from a source outside then tank is another possibility.  A number of common household products, insecticides and sprays can be deadly for fish.  These products could be drawn into the water via the air pump.  Never be tempted to use such products in part of the home, or next to a pond, where they could indirectly cause harm to the fish.

Always consult a vet if you have ANY reason for concern. 

 

 

JSPCA working to

“prevent cruelty, promote knowledge, provide for aged, sick, lost and unwanted animals.”

 

Jersey Society for the Prevention of Cruelty to Animals (Inc.)

Founded 1868 – Incorporated 1936

89 St Saviour’s Road, St Helier, Jersey JE2 4GJ         

Tel: 01534 724331          Fax: 01534 871797

E-mail: info@jspca.org.je          Website: www.jspca.org.je

 

References and further reading:

  • BSAVA Manual of Exotic Pets, fourth edition.

  • London Zoo, Zoological Society of London Fact Sheets.