As with any other type of pet, there are some basic considerations involved in the care of goldfish. Before you purchase any type of pet for the first time, you need to do a little research to find out about its behavioral characteristics, required living conditions, and feeding requirements. Goldfish are no different.
In the past, the care of goldfish often consisted of putting one or two of them in a small bowl and feeding them once a day. Under this kind of care, goldfish generally didn't live terribly long, certainly not the 10 years or more one could expect of them. Some of the more exotic, and more fragile types, wouldn't live long at all. Goldfish like clean, cold water, and prefer life in an outdoor pond more so than in an aquarium, and certainly much more so than in a small bowl. While goldfish are happier having a companion or several companions, they require more space than do tropical fish. Figure between 10 and 20 gallons per goldfish, bearing in mind that the common types are generally larger than the exotic types, and need closer to 20 gallons per fish.
Although you can mix common types and exotic types of goldfish together, you should exercise a bit of caution. Some exotic types, particularly those with telescopic or bubble eyes, are susceptible to injury in crowded conditions. Also, though goldfish are generally not very aggressive, there can be pecking orders established during feeding, and sometimes more timid types can lose out. If you do mix several types together it won't hurt to check from time to time to see if anyone is being picked upon.
Goldfish are also curious, and more intelligent than commonly believed. They like to have a variety of things in the water that they can swim around and through. Initially then, take into account that where you are planning to keep a goldfish could be its home for many years, and you want to do what you can to make it a good home. Once you have a good home, whether it's a pond or an aquarium, you should add a small air pump to keep the oxygen level high and, if an aquarium, put some clean washed gravel on the bottom, preferably gravel intended for just that purpose. Add a filter to help keep the water clean, a few plants, some structures to make life a little interesting, and you're ready to add the fish.
To avoid disease and illness the water must be kept clean. It's best to change the water, but not all at once, unless the existing water is really harmful to the fish. Existing water normally contains some bacteria that is actually helpful. The gravel will need to be taken out and washed on occasion, as it will normally get dirty fairly quickly.
As far as feeding is concerned, the key is to avoid overfeeding. The fish will often eat as long as there is food available, and if fed too much will sometimes get fat, but more often than not become ill. Overfeeding is a major cause of illness in goldfish. Also, if you overfeed fish that are in an aquarium, some of the food that is not eaten will settle to the bottom and become a breeding ground for bacteria.
As far as what kind of food to feed a goldfish is concerned, there are several choices, and there is nothing wrong at all with giving your fish a little variety. Dry goldfish food, the kind you find in the pet store or supermarket, is a good source of nutrition, and comes in flakes which float on the surface, or pellets which sink to the bottom. You can also have plants in the aquarium or pond that they can nibble at, and goldfish also like live food, brine shrimp and certain types of worms being examples. One needs to be a little bit cautious with live food so that undesirable agents, such as bacteria or worms, are not introduced into the container. Goldfish will also eat vegetable matter such as small bits of lettuce. In the wild, goldfish eat a variety of vegetation and insects, including mosquitoes and mosquito larvae.
Given good quality water, sufficient room, food (but not too much), and perhaps a companion or two, you've off to a good start as far as the proper care of goldfish is concerned. About the only things remaining are to monitor the fish often enough to be able to detect if there are any problems developing, and finally, bring yourself up to speed regarding symptoms and treatments should disease or illness enter the picture.
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