The goldfish (Carassius auratus auratus) is large freshwater fish that was originally native to China. Its ancient ancestor is believed to have been the Chinese Crucian carp, though recent research seems to indicate that they may actually be descended from Prussian carp.

The goldfish is one of the oldest domesticated fish in the world, with only one fish that may have been kept longer – the unassuming weather loach. There are records of goldfish being kept in ponds and containers as far back as the 3rd century A.D, and by the 7th century, they were being kept in containers to show off their brilliant colors.

Today, goldfish come in a dizzying array of shapes and sizes. There are several varieties that still closely resemble the common goldfish – such as the comet and shubunkin. But when it comes to fancy goldfish, it’s a very different story.

Fancy goldfish have been selectively bred to the point where they are almost unrecognizable as fish – never mind goldfish. A few species are almost incapable of surviving without constant attention from their owner, and in the case bubble eye goldfish, will literally pop if you put anything sharp in their aquarium.

That’s not to say that all fancy goldfish are inbred monsters, one step away from requiring diapers and round the clock spoon feedings. Most of the more common ones like black moors, orandas, veiltails and lionheads still make an excellent addition to any fish collection, and don’t require much in the way of extra care.

It should come as no surprise that there are big differences in both life span and size for common and fancy goldfish. Common goldfish, comets and shubunkin will grow much larger and generally have longer life spans than fancy goldfish.

A few very large common goldfish have been recorded at lengths exceeding 18 inches (45 cm), and can easily live more than 20 years in a home aquarium. Fancy goldfish on the other hand, usually only grow to a maximum length of 8 inches (20 cm), and will usually live for around 10 years – though several varieties have much shorter life spans.

Housing

Because of the vast differences in care requirements for common goldfish and fancy goldfish, this section is broken into two parts.

Common Goldfish, Comet Goldfish and Shubunkin

Common goldfish, comet goldfish and to a lesser extent – shubunkin goldfish are all very tough fish. They can survive in poor water conditions, with low levels of oxygen for extended periods of time. But just because they can survive in these environments, doesn’t mean that they should ever be kept in poor conditions. And what that means is NO goldfish bowls.

Goldfish can quickly grow to aquarium busting sizes, and they should never, ever be kept in a goldfish bowl. Their enormous size, combined with their prolific pooping, quickly turn a goldfish bowl into a death trap for them. No amount of water changes can keep their tank water from becoming toxic and either making the goldfish ill or outright killing them. Even if it survives for any length of time, it will become stunted and sickly, and will likely never reach maturity.

So if you can’t keep them in fish bowls, what can you keep them in? Unfortunately the answer to this question puts goldfish out of reach for most responsible aquarists – they need to be kept in some of the largest aquariums available. The bare minimum tank size should be around 55 gallons (210 litre), and a trio of goldfish would more realistically need a 75 gallon tank (280 litre).

And because their life seems to consist only of eating, pooping, and then eating some more, they will need a significant amount of filtration in their aquarium to keep them healthy. On my goldfish tank, I have an HOB (hang-on-back) filter and a large sponge filter to provide extra biological filtration. Some people choose to use two HOB filters or use the more expensive, but usually superior canister filter.

Something else that is very important to the health of a common goldfish, is that they need to be kept in a cold water aquarium. Their aquarium should never be heated, and it’s important to keep the temperature in the low 70s F (21 C) range during the summer. If they are kept at higher temperatures for any length of time, they may suffer nerve damage.

Fancy Goldfish

Fancy goldfish are much more delicate than common goldfish, and in most cases, won’t last a day in poor water quality. It’s even more important to never put a fancy goldfish in a goldfish bowl, and while they don’t need as large a tank as common goldfish, they still need a spacious, well filtered tank.

They should always be provided with at least a 29 gallon tank (110 litre) and to be on the safe side, I usually recommend that at least a 45 gallon (110 litre) tank be provided. You should also never mix fancy goldfish with common goldfish. Fancy goldfish are often poor swimmers, and they will have trouble competing for food with any goldfish with a natural body shape – which means in any mixed tank, you will have to choose between overfeeding to ensure that the fancy goldfish get some food (never a good idea), or just let go hungry (also a bad idea).

When choosing a filter for fancy goldfish, an HOB (hang-on-back) filter is usually the best option for them. It boasts both a reasonable price and excellent filtration, but you do need to be careful not to provide too much current. As already stated, they aren’t very strong swimmers and try to avoid current if they can. Because their water needs to be kept as pristine as possible, I also use sponge filters in conjunction with a high quality HOB filter.

Unlike common goldfish, fancy goldfish tanks should be heated if they fall below 60 F (15 C) in the winter. They are not capable of surviving in a true cold water tank, but also shouldn’t be subjected to overly warm temperatures during the summer.

Substrate

It’s important to select the right substrate for goldfish, since choosing the wrong one will often result in their deathes. Goldfish are constantly on the lookout for food, and as soon as they are large enough to fit gravel in their mouth, they will start to sift through it looking for food.

The problem arises from the fact that gravel sucked into their mouthes may become lodged. While this is less of a problem with larger goldfish, for smaller ones this can be deadly when they can’t get it out.

The easy solution to this problem is to use river rocks or play sand for the substrate in a goldfish tank. I personally prefer play sand, since it looks stunning when kept clean, and only costs a few dollars a bag. River rocks also work well, but you need to be careful to really clean the area around the rocks during weekly maintenance. Uneaten food and fish excrement has a tendency to build up around large rocks and can quickly foul the water.

Feeding

For a fish with an appetite as large as a goldfishes, it’s surprisingly hard to feed them properly. The problem isn’t that they won’t accept food, but that they need a very plant heavy diet. They won’t do well if fed a strictly flake food diet (unless they are herbivore flakes).

If a goldfish is fed only regular fish food flakes, they may develop a condition called bloat – which doesn’t end well for the goldfish. This is especially prevalent in fancy goldfish, but can also occasionally strike common goldfish. When a goldfish develops bloat, its belly swells up and it often becomes unable to swim.

This can be avoided through regular feeding of vegetables, such as blanched zucchini medallions and shelled peas, or by switching your fish food to a more herbivore friendly food. My personal preference is spirulina pellets, with regular feedings of a diverse range of vegetables.

They can also occasionally be fed live or frozen food as a treat. Their favorite frozen foods are blood worms, brine shrimp and daphnia. When it comes to live foods, the easiest to obtain are usually blackworms (tubifex in Europe) or daphnia. Brine shrimp are also easy to obtain, but don’t have much nutritional value unless they are gut loaded prior to feeding.

If your goldfish contracts bloat, there is usually an easy remedy (assuming it’s not related to parasites or bacteria). To begin treatment, they should be fed several servings of shelled peas, and if the bloat has progressed to the point where they can’t move, the peas should be hand fed to them. This will normally clear up the bloat and the goldfish should be swimming fine within a day or so.

Breeding

Most goldfish will breed on their own in captivity and you just have to wait until they reach maturity. With that being said, like most cold water fish, they will require a trigger for breeding. If their tank is unheated and they are in a room with natural light, the normal changes in daylight and temperature during spring are usually enough to trigger breeding.

However, if you need to trigger breeding on your own, you will have start by lowering the temperature and shortening the tanks light cycle for a few months. Both the temperature and the amount of light should be reduced for at least three months. The goldfish should only be receiving about 8 hours of light a day during this time and the temperature should be in the low 60s F (15 C) if possible.

After several months have passed, the light and temperature should be slowly increased over the course of 4-5 weeks. The temperature should slow be increased until it is approaching 70 F (21 C) and the light should be increased in step with the temperature, until they are receiving at least 12 hours of light a day.

The increase in temperature and light will usually signify spring to the goldfish, and if they are mature enough, they will start to breed. If your goldfish don’t breed at this point, they may either be too young, or you need to start the cycle over again.

Once spawning has been successfully triggered, the male will chase the female and will nudge her until she releases her eggs. The female will generally scatter her eggs into any live plants in the aquarium, or more likely in a goldfish tank – fake plants.

The goldfish should be removed from the tank after they have mated, since they may eat the eggs and will eat any fry that they can catch. The eggs will take a few days to hatch, and the fry are usually free swimming within a week.

The fry won’t take on the goldfish color for up to a year, and some of the fry may have a natural dull brown coloring. They will grow very quickly in the aquarium and can be fed baby brine shrimp, microworms or any commercially available fry food until they are large enough to accept powdered flake or pellets.

Plant Compatibility

There’s a reason that you don’t see many pictures of planted goldfish aquariums – they love to eat just about any aquatic plants. Most plants will only provide an expensive salad bar for your goldfish, though there are a few plants that “may” survive.

The one plant that I’ve achieved success with in a goldfish aquarium is Java moss. While they may move the moss around, they generally won’t eat it. The same goes for Java ferns, hornwort and in some rare cases – Amazon swords (though they will get munched on a bit). They generally won’t eat them, but they may move them around, which is very unhealthy for the rooted plants.