Goldfish have long been, and still remain, one of the most popular family pets available. They're attractive to look at, widely available, highly affordable, and fairly easy to look after. A variety of carp, Goldfish are one of the earliest domesticated fish, and can be kept in aquariums or ponds.
Goldfish are available in a variety of different colours, shapes, and sizes. Traditional or “common” goldfish are usually yellow, orange, red, white or black in colour, although patterns are common. They usually resemble a small carp in appearance. However, other varieties of goldfish can be quite distinctive in appearance. Some have large, decorative tailfins, while others have large “goggle” eyes. Some specialised varieties have rounded bodies or hoods, and others have “pom poms” around the head region. For the most part, however, these varieties are easily identifiable as subsets of traditional goldfish.
Goldfish are most commonly kept in a fishbowl or fish tank, or in a pond. Goldfish tend to thrive in ponds, and such fish will often live longer than their tank-kept counterparts. They are quite hardy and tend to be relatively unaffected by changes in temperature. Still, ponds need to be adequate in terms of size and depth, and need to have sufficient plant life to ensure that the water receives appropriate oxygenation. Plants are also essential as a food source for goldfish.
Pond-kept goldfish can be helpful in reducing the incidence of mosquitoes and other insects that breed in still waters. Pond dwellers may require some additional protection from predators.
Goldfish kept in fishbowls or fish tanks need more care than those kept in a fish pond. This is because the refuse created by fish food and by the fish themselves can quickly dirty tank water. The water can become toxic, causing harm to the fish. For this reason, tanks and aquariums should be cleaned on a regular basis. Owners should also be mindful of temperature changes when it comes to tank-kept fish, as the small surface area of these tanks means that the temperature of the water can quickly rise or fall, causing a shock to the fish.
Goldfish often reproduce in a captive environment. Upon reaching maturity, which usually occurs at a year or so of age, the fish will lay eggs, which then attach to vegetation within the tank. These eggs will hatch into brine within a few days. Note that many highly specialised breeds of goldfish are less likely to breed in captivity.
The two most common types of goldfish food are flakes and pellets. However, goldfish can also be fed blood worms and brine shrimp. Owners should be careful not to over feed their fish, as goldfish will continue to eat even when no longer hungry. This behaviour can cause ill-health in the fish. The appropriate amount to feed a fish is around 1-2% of the fish's body weight. This usually means a piece of food that is comparable in size to the fish's eye. This portion should be divided for feeding over several sessions throughout the day.
Goldfish behaviour varies depending on the type of environment they're kept in. Goldfish often swim in schools, and are avoidant, meaning that they'll shy away from any potential threats. They tend to react favourably to their owners, as they associate the approach of their owners with being fed. In contrast they will usually swim away from strangers. Contrary to popular belief, goldfish have a memory-span of several months.