1. Where did / do goldfish come from?
The ancestor of the goldfish - a small, plain carp - came from south/central China. Nearly 2000 years ago, the Chinese started to selectively breed these fish, at first in small ponds and later in even smaller containers such as large clay pans, to develop certain features, such as colour, body shape, etc. Today, millions of goldfish are bred all over the world each year (see breeding).
2. How many different kinds of goldfish are there?
After 2000 years of intensive selective breeding, at least dozens, possibly over a hundred. Goldfish varieties are classified by colour, body shape, finnage and outgrowths of the head/eyes. New varieties are being developed all the time. Personally, I dislike the more outlandish varieties, particularly those with baggy eyes such as bubble eyes and celestials, but each to his own. For the purposes of care, it's only necessary to divide varieties into two types:
Deep-bodied varieties such as moors, orandas, veiltails, etc.
Shallow-bodied varieties with the same shape as ancestral goldfish - common goldfish, comets, shubunkins, etc.
3. How long do goldfish live?
Possibly for 40-50 years! There are lots of records of goldfish living over 30 years, but this is exceptional. A typical well cared for goldfish will easily live for ten years. This means that when you buy a goldfish, you are making a long term commitment to the animal (read this and this).
4. What should I keep my goldfish in?
There are two choices, an aquarium or a pond. Bear in mind that goldfish are carp which can grow to 18 inches long and several pounds in weight! Goldfish are quite social and benefit from being kept in groups of three or more. For this reason, I would never keep goldfish in an aquarium of less than two feet in length - three feet is better! Allow one square foot of surface area (depth is irrelevant) per medium sized goldfish (up to four inches long) - more as they grow. Thus a 24x12x12 inch tank (15 gallon) can accommodate two medium sized goldfish, a 36x12x18 inch tank (29 gallon) can accommodate three medium sized goldfish, etc.
Filtration does NOT allow you to cram more goldfish in the same space, but may help you maintain better water quality and prevent disease. At these stocking levels, goldfish will be quite happy in unfiltered aquaria - save your money and enjoy a silent tank without irritating noise - but you will need to perform regular partial waterchanges, e.g. 20-30% every week. The Chinese originally kept goldfish in shallow clay pans - large surface area and with frequent waterchanges of around 50% a day. Goldfish are also happy in planted tanks, as long as these are set up with goldfish in mind.
Ponds need not be large, but goldfish should not be overwintered outdoors in ponds with a water depth of less than two feet, except in areas where ice never forms. Also, small ponds must be protected from strong sunshine or fish will die due to overheating/lack of oxygen. Deep-bodied varieties are not suitable for ponds and should only be kept in aquaria. If I wanted to torture a goldfish (I don't), I would:
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Keep either one solitary fish in a glass bowl, or at least six fish if the bowl was particularly small!
Feed it on an exclusive diet of dried food - it's especially good either to let young children feed the fish unsupervised (try to make sure they dump the whole container of food in regularly), or to tip food into the bowl every time you walk past, Because it looks hungry.
When the water got so cloudy I couldn't see it any more, catch it with my hand and dump it in the washing-up bowl (not washed so containing lots of soap residue), scrub out the fishbowl until it was sparkling, fill it directly from the tap, plunge the fish back into the bowl, ensuring the difference in temperature was as great as possible.
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5. What kind of water do goldfish need?
The ideal water for goldfish is clean, moderately hard, slightly alkaline and slow moving. In most places, tapwater is fine. If your water company adds chloramine to your tapwater, you may need to add a water conditioner when you perform waterchanges. If only chlorine is present, there is no need for any additives if you only perform partial water changes (less than 50% of tank volume). If your tapwater happens to be very soft/acid, use a mixture of 50% coral gravel and 50% plain gravel on the floor of the tank. This will gently harden the water and increase the alkalinity without harming the fish.
If you use a filter (not essential if your tank is not overcrowded), the outflow should be diffused so it does not blast the fish around the tank.
6. What should I feed my goldfish and how much?
Goldfish are pigs, sorry, I mean omnivores - they will eat anything, and as much of it as they can get. More goldfish are killed by overfeeding than any other cause. Only feed as much food as they will completely consume in five minutes. If any food is left after that time, siphon the excess out. That's a hassle - so don't overfeed in the first place, you're wasting your money and hurting your fish. Remember, more goldfish are killed by overfeeding than any other cause. How often to feed? 2-3 times a day is ideal as long as you only feed a small amount each time, but once a day is OK. It's a good idea to skip feeding one day a week - this helps digestion and improves water quality. I absolutely promise you: YOUR FISH WILL NOT STARVE! Remember, more goldfish are killed by overfeeding than any other cause (getting the idea now?). Cold-blooded animals like fish can safely go for long periods without food.
What to feed? The basis of their diet should ideally be a nutritionally-balanced dry goldfish food in stick or pellet form (flake food tends to be messy for adult goldfish). In addition, your fishes health will be greatly improved by additions of fresh food. Goldfish are primarily herbivores (vegetarians), so the bulk of their diet should be vegetable based.