It is a serious fish disease that can eat into the body of the fish after destroying all of a fin, leading to death.  Even before it gets to that stage, it can lead to severe complications.  Very often, a fungal infection takes hold in the affected fin, making treatment even more problematic.

Symptoms

The first signs of tail and fin rot are red streaks in the fins.  The edge of the fin will then lighten, before it starts to rot away and gain a ragged appearance.  Small bleeds may also be present.

Biological symptoms include variations in the levels of calcium and haemoglobin in the fish’s blood.

If a fungal infection occurs, the edge of the fin may be smoother i.e. get eaten away in a more uniform manner - and have a white edge.

Causes

Tail and fin rot is caused by bacteria.  The specific bacteria that cause the disease are common and found in most bodies of water, including ponds and aquariums.  The problem arises when the fish are subjected to an external event or environment that make them susceptible to infection.

By far the most common factors are poor water quality (especially raised levels of ammonia and nitrite), and direct trauma to the tail and/or fins.  Direct trauma can be a result of nipping by other fish, bad handling by humans, or sharp edges on plants and ornaments in the water.  The stress of any of these events leaves the fish open to infection.

There are three different bacteria that can cause tail and fin rot:

1. Aeromonas - a rod shaped bacterium that can also infect humans, often resulting in the need for amputation.
2. Pseudomonas - another rod shaped bacterium that has “superbug” strains found in hospitals that cause necrotizing inflammation in humans.
3. Flexibacter - a bacteria that normally only affects fish, and is best known for strains that are bright yellow to the naked eye when colonies grow large enough.

To be precise, tail and fin rot is not a disease itself.  It is actually just a symptom of infection with one of these bacteria.

What the bacteria do is congregate in the intestine of the fish.  They then produce a mucous that contains molecules that are toxic to fish.  These toxic substances are absorbed through the wall of the intestine in much the same manner as essential nutrients, thereby entering the bloodstream.

The red streaks that are the first sign of tail and fin rot are caused by small blood vessels in the fins breaking apart under the action of the poison, and releasing blood.

Without a blood supply, the fins quickly lose their colour, break down and rot away.

While all this is happening on the outside of the fish, similar processes are destroying the blood vessels of the stomach, liver and kidney.

To start with, there are two basic colour types: metallic and calico.

Calico

Calico is the name given to the colour pattern most commonly found on shubunkin goldfish.  It is an irregular pattern of orange, yellow, red, black, brown, blue, violet, pearl, white and/or silver.  As long as there are three or more of these colours in a random pattern, the goldfish is calico.

Another feature of calico colouring is that some of the scales are shiny, some are translucent, and some are velvet in appearance.  The shininess of goldfish scales depends on the amount of a substance called guanine present in the scales.  The more guanine, the more reflective the scale.

The blue and violet colours that can be found in calico goldfish are actually black pigments deep under the skin that appear coloured when viewed through the pearly coloured skin.

Metallic

The term metallic is slightly misleading, as it does not necessarily mean reflective all over.  Metallic coloured goldfish can have shiny or velvety scales.

Metallic colouring is divided into two types: self-coloured and variegated.

Self-coloured means nothing more than the same colour all over.  The colour can be orange, yellow, red, black, brown or blue.

Variegated simply means that the goldfish has more than one colour, and both sides of the fish are almost exactly the same pattern.  As well as the list of colours available in self-coloured fish, silver and white can be present in variegated fish.  A good example of variegated colouring is the redcap oranda.

Almost everybody knows it, but plenty of people do it.  Goldfish that live in a bowl do not get enough oxygen, are exposed to disease, and usually die young.  If they are unlucky enough to survive into adulthood, they will be too big for the bowl and suffer from deformities.  It is cruel.  Don’t do it.

2. Put in a blender

A fairly old story, but nonetheless shocking.  An artist called Marco Evaristti had work displayed at an exhibition in the Trapholt Art Museum in Kolding, Denmark in 2003.  His artwork was a blender with 2 live goldfish in it, and an open invitation to anybody to turn the blender on.  Somebody did, liquidising the goldfish within a second.  Mercifully it was a quick death, but unnecessary, crass, attention-grabbing and cruel.

3. Sealed inside a novelty keyring

Street traders in Qingdao, China have been selling novelty plastic keyrings with a little bit of water and a goldfish inside.  The keyrings are made of transparent plastic with a picture of Huanhuan - an Olympic mascot - printed on it.  Needless to say each goldfish has little or no room to swim in, hardly any oxygen, and is destined to die of suffocation.

Specifically, the oranda is one of the veiltail goldfish.  What this means is that the two layers of the tail fin are separate, nearly as long as the body, and are not deeply forked.  The body itself is deep rather than long in veiltail goldfish.

Oranda goldfish come in many different colours.  They can be red, orange, yellow, black or blue; or a combination of these colours.  They can also be “calico,” which is the technical name for the colours found on shubunkin goldfish.  Another sub-variety of oranda is the redcap oranda, which is all (or almost all) white apart from the growth on its head being vivid red.  The photograph shows an oranda in the foreground, and a redcap oranda in the background.  The extent of the head growth in redcaps is usually less, and generally does not extend below the eyes.

Being fancy goldfish, orandas do not compete well against long-bodied goldfish.  They need to be kept with other slow swimming fancy goldfish to give them an equal chance at feeding time.  They are also sensitive to changes in water temperature, and do not like water that is too cold.

The most common problems experienced by oranda goldfish are unsurprisingly to do with the head growth.  Small particles that find their way into the folds of the growth can end up causing bacterial and/or fungal infection. Also, because of the body shape, swim bladder problems are more common than in long-bodied goldfish (although this is a problem with several varieties of fancy goldfish, not just oranda).

Apart from that, a well managed and carefully monitored tank containing orandas shouldn’t be a problem.  Oranda goldfish are a genuinely visually interesting goldfish variety, and the head growth on non-redcap orandas can give them a facial expression that makes them that little bit different from other fish.  Redcaps of course are visually striking, with their high contrast colours.  No matter what sort of oranda is in a tank, they are sure to be a talking point.

The lateral line runs down each side of most fish (and amphibian larvae), from the gills to the tail.  It is usually visible as a faint line of dots about halfway down the sides of the fish.  The exact appearance of the lateral line varies from species to species, and these differences are sometimes used to help distinguish closely related fish species.

On a smaller scale, each dot on the line is called a neuromast.  A neuromast consists of a bunch of hairs surrounded by a gel cap.  This whole structure sits in a little hole in the side of the fish, and is connected to a nerve.

The general purpose of the lateral line is to detect changes in water pressure.  The gel cap transfers the pressure changes to the hairs, and on to the nerve, working much like the hairs of the human inner ear.

For example, when a fish is swimming normally with clear water ahead, the pressure is consistent and as expected, a bit like the wave that forms in front of a boat, only in 3 dimensions.  So when the fish is heading for the glass of an aquarium, the pressure of the water flowing over the head and body will change as the shape of the wave changes.  This enables the fish to avoid such invisible objects.

Changes in water pressure will also be caused by other fish swimming nearby, and the lateral line has also been shown to play a part in schooling behaviour in some fish species.

Other species can detect and accurately locate insects on the surface of the water, without having to rely on sight.  This is a good thing in an environment where light does not behave as predictably as in air.  It also means the fish does not need specially adapted eyes that point upwards, and can use them as normal i.e. seeing morsels in close view in front of the fish, and looking out for danger to the sides.

Low frequency sounds are also detected with the lateral line, simply because they cause changes in the water pressure.

Finally, in sharks the lateral line is used to detect changes in electromagnetic fields in water.  A very useful tool for hunting prey.

There are a number of practical steps that can be taken to control pond algae, most of which form part of basic pond management anyway.

Pond Construction

By following the steps outlined in the earlier blog post Build the Perfect Goldfish Pond, pond algae will already be less of a problem.  By making sure the pond is not positioned where a lot of debris will fall into it, there will be less nutrients for the algae to use for growth.  Using a black liner to absorb sunlight rather than reflect it into the water also deprives algae of the conditions it likes.  If the pond has sloping sides leading down to a bottom level, it makes the job of collecting any debris that does fall in easier, as it will be more localized.  Finally, have a pond that is deep enough to prevent strong sunlight penetration, and large enough to reach its own level of ecological balance will also work as an excellent preventative measure.

Plants

Plants can be used to provide shade over the water where long periods of direct sunlight are a problem.  Water lilies are the obvious example, but there are many different types of aquatic plant that can be used.  Plants also have the added effect of using up the nutrients that algae would otherwise thrive on.

Cleaning

It is a fairly obvious point, but floating plant debris should be removed from the surface of the pond as often as it appears.  If it remains long enough to sink to the bottom it starts to produce the nutrients that fertilize the algae, and is more hassle to remove.

Isolation

If fertilizers are used on surrounding lawns, it is vitally important to prevent run-off from the lawn into the pond.  If the pond is at a lower level than any part of the lawn, some sort of barrier needs to be  in place that will direct contaminated water around the pond.  Garden fertilizers are designed to make green things grow very quickly.  They can cause disastrous algal blooms in goldfish ponds.

Barley Straw

When barley straw is placed in water it starts to decompose.  Chemicals released during the decomposition process are effective in stopping algal growth.  Bunch it inside a net - a couple of large handfuls should do for an average sized pond - and when it turns black its job is done.  Repeat the process as necessary to help control algae.  Barley straw extract is also available as a commercial product.

Skimmer

A skimmer is a mechanical device, powered by electricity or battery that removes floating debris from the surface of a pond.  There is no need for one unless manual surface cleaning doesn’t take place.

UV Filtration

Ultraviolet lamps can be purchased which are then placed in the pond water.  As the algae suspended in the water pass over the lamp they are exposed to UV rays.  These rays destroy algal DNA, and the result is usually a very clear pond.

Chemical Treatment

Anti-algal chemical treatments are available and offer a quick and easy solution.  Although generally not harmful to goldfish, they can be poisonous to frogs, snails and insects that help create an ecological balance and increase biodiversity in the pond.  As well as that, they are not always effective against all (over 17,000) types of algae.

However, that is in a natural setting.  When a heron visits a goldfish pond, it doesn’t need any patience.  There is crystal clear water with brightly coloured goldfish that can be picked off at will.  No need to wait for a fish that is the same colour as the murky water it is swimming in.

Apart from the obvious problem of quickly removing goldfish from a pond, herons cause a number of other problems for goldfish.   Firstly, they are disease carriers.  Secondly, if they don’t introduce a disease to the pond, an attack could increase stress levels in the remaining goldfish to levels that make them susceptible to disease.  Thirdly, they can spear a goldfish only to discover it is too big to swallow.  When that happens, they leave the goldfish by the side of the pool to die.  Whether or not suffocation kills it before the stab wound, it will die in agony.

Therefore it is very important to do everything possible to prevent heron attacks, and there are a number of methods available.

Hiding Places

Put some sections of pipe or upturned flower pots with entrance holes in the pond.  Goldfish can use these to shelter in when they see a heron at the surface of the water.  Unfortunately the goldfish will need to have been attacked at least once before knowing what a heron looks like, and taking advantage of the hiding places.

Netting

Netting stretched tightly over the surface of the pond will prevent herons taking goldfish.  The problem with this method is that it is unsightly and makes feeding the goldfish more awkward than it should be.  Having said that, a net should be used for a while after the first heron attack.  This is because the heron will be sure to return for more easy pickings.

Fishing Line

Herons usually won’t land in the pond, because they know it will scare the goldfish.  They prefer to walk up to the pond and launch a surprise attack.  A length of fishing line across the path of the heron about a foot (30cm) away from the pond and a foot off the ground will give a heron a fright when it trips over it.  The RSPB recommend using two lengths at about 6 and 12 inches off the ground.  However, herons will get wise to this trick, and use other approaches.  Then the whole pond will have to have a perimeter round it.  Eventually the heron will learn to land inside the perimeter, or on sturdy plants inside the pond.  If the pond is quite large, they will most likely land in the water anyway.

Scarers

Various forms of scarers can be used.  Some rely on a constant flow of water causing sudden movement on a hinge, others use trip-wires or infrared detectors to set off loud bangs or squirt jets of water.  Whatever method a scarer uses it will most likely be expensive, and a patient heron will eventually get used to it.

Plastic Herons

Plastic herons are sometimes placed in ponds to make real herons think the territory has already been claimed.  Many goldfish pond keepers dispute this, and point to the fact that herons looking for a mate will very often land beside a plastic heron, realize it’s not real, then eat all the goldfish.  On top of that, a hungry heron won’t care if another heron appears to stand between it and a meal.

Routines

Probably the most effective long term method of preventing herons taking goldfish is to train the goldfish when to come to the surface of the pond.  Always feed them at the same time every day, so that they eventually get to know when to come up.

On the other hand, break up the routine of going to the pond.  Herons watch and wait before deciding when to attack a goldfish pond, and will not do it when they think a human will be in attendance.  They will work out when the coast is clear and fly in.

Approaching the pond at unpredictable times but feeding at predictable times means that the goldfish will know not to surface every time they see a figure at the side of the pond.

Obviously if a house is left unattended at regular times for long periods this method will not work.  Neither will it work at the crack of dawn when most people are still in bed.  However, if it is done when possible it is very effective.  It foils the heron’s plan at the earliest stage - before it gets anywhere near a pond.  Outwitting the heron is something no fishing line, net or banger will ever be capable of.

Summary

It’s a game of cat and mouse.  Herons will always be attracted to goldfish in a pond.  Hiding places should be provided as a matter of course, and trip-wire may be necessary at some point.  However, the main thrust of any anti-heron activity should be to make the pond more hassle for the heron than it is worth at another pond.  Herons will visit a number of ponds looking for an easy meal, so a pond that gives them a bit of hassle should quickly get taken off the list.

However, other herons will take a look, so it’s important to remain vigilant and keep on top of the situation.

The shubunkin is a single-tailed fast swimming goldfish that is happy enough in either a pond or aquarium, and is an ideal companion for common goldfish and comets.  Like all goldfish, it thrives on a varied diet.

Another advantage of the shubunkin is its liking for bottom feeding.  This helps keep the goldfish tank clean as they will clean up any uneaten morsels that go un-noticed by common or comet goldfish.

They can live up to 10 years and grow to 30cm (12″) in length.

There are three types of shubunkin goldfish, easily distinguished by the tail fin.

London Shubunkin

This shubunkin is actually a variation of the common goldfish, the only difference being the colouring.  They have a compact body and a short tail fin with a shallow fork, exactly the same as the common goldfish.  This is the most common type in the UK.

American Shubunkin

Sometimes called the Japanese shubunkin, this type is shaped like the comet goldfish.  It has a more slender body with longer fins.  The tail fin is pointed with a deeper fork and can grow to the same length as the body.  This type is the most common in North America and are shown in the photograph above.

Bristol Shubunkin

This type was developed by the Bristol Aquarist Society and has a beautiful big heart-shaped tail with two rounded lobes. It’s body shape is more like the common goldfish, but it has longer fins.  The best place to see photos of it is the Bristol Aquarists Society Bristol shubunkin page.

Shubunkin goldfish are an ideal way to break the mould a little bit in a pond or aquarium that has uniformly coloured common and comet goldfish.  Although not to everybody’s taste (a lot of beginners think they are diseased), the different colours - especially blue and violet - can make an aquarium a vastly more interesting place.

Preparation

Once ick has been discovered in a tank, the first task is to prepare the tank for treatment. If any filters contain activated carbon for chemical filtration, remove it. The activated carbon will remove the medication from the water. UV sterilisers and protein skimmers should also be switched off in order for the treatment to work effectively.

The water in most goldfish tanks is at room temperature (roughly 18 Celsius/65 Fahrenheit), so there is no general requirement for a thermostat. However, using one to gradually increase the water temperature by half a degree celsius every day will reduce the length of treatment. This is because the ick is only treatable during the theront (free swimming) phase of the life cycle. Due to the fact that an increase in temperature speeds up the life cycle, the theront phase will arrive quicker at higher temperatures.

If possible, bring the water temperature up to 26 Celsius (80 Fahrenheit) and the treatment will be over in 10 days. Keeping the temperature low will mean the treatment will need to continue for 6 weeks. One word of caution though - when the ick life cycle takes a week, a new dose of parasitic infection comes round every week. If anything is wrong with the treatment program it could result in heavy infestation, and goldfish dying off quickly.

Finally remove any snails, and check if any aquarium plants present are sensitive to the recommended treatement - malachite green.

Treatment

Malachite green is a widely available chemical treatment for ick. Other chemicals that can be used are formalin, copper, quinine hydrochloride, methylene blue and sodium chloride. However, non of these are any better than malachite green, which has the advantage of been successfully used to treat ick for many years.

Follow the dosing instructions on the label to the letter, taking care to avoid eye and skin contact. Malachite green leaves a stain on almost everything it touches.

At the ideal temperature, continue the treatment for 10 days. This will ensure that the theront phase of the ick life cycle will have been exposed to the malachite green. During the trophozoite and tomont phases, the chemical will have no effect on the parasites. In both cases they are enclosed in protective cysts that are impervious to any known treatment.

Although the life cycle only takes a week at this temperature, the treatment should go on for 10 days in order to make sure that all traces of ick have been removed.

It is worth noting that the treatment for ick treats the water. When treating the vast majority of goldfish diseases it is the goldfish itself that is treated. However ick can only be killed when it is vulnerable, and that is when it is out in the water.

Prevention

As is the case with every goldfish illness, prevention is better than cure. Make sure the water is tested regularly, feed the fish a balanced diet, change the water regularly and don’t put too many goldfish in the tank. These measures should be par for the course in every single goldfish tank and pond.

Also, never buy aquarium plants that are in a tank with fish in the pet shop. Tomonts stick to plants, and a single one provides an easy passage for up to 1000 individual parasites.

When bringing a new fish home for the tank, put it in a quarantine tank for whatever length of time the ick life cycle takes at the water temperature of the quarantine tank.

Ick is common and deadly, but following the advice above will save goldfish from the disease, and bring them back to rude health as quickly as possible.

Trophozoite

This is the phase of the ick life cycle when the parasite is living in the skin of the goldfish. It is a spherical shape with a cup shaped mouth at one end. The mouth contains very fine hair-like structures called cilia, that beat rhythmically and continuously inwards. These cilia scrape tissue from the body of the goldfish and pass it into the mouth.

Goldfish produce a natural reaction to the trophozoite - they surround it with a hard casing that forms a cyst. It is these cysts that are the most noticeable symptom of ick - the appearance of being sprinkled with salt.

Depending on the temperature of the water, the trophozoite grows to between 0.1mm and 1mm wide, and after about a week it falls off the goldfish. It swims in downward spirals to the bottom of the aquarium, or sticks to a plant or ornament.

Tomont

Once the released trophozoite has settled, it absorbs its own mouth and secretes a gel around itself, becoming known as a tomont (or trophont). It then starts to replicate inside the gel casing. The cells produced by the first few divisions form an internal wall on the gel casing, but the rest of them develop into parasites.

The number of cells produced in the tomont can reach 1000, and will usually be at least 600. This phase of the ick life cycle will be complete in anything between 8 hours and several weeks, depending on water temperature.

When complete, the tomont bursts and releases the individual cells called theronts. These look for goldfish to burrow into.

Theront

Theronts (also known as tomites) are microscopically small and oval in shape. They are good swimmers and move about the aquarium until they find a goldfish to latch on to and burrow into.

They swim with cilia and are thought to burrow into goldfish skin using these cilia, and possibly a combination of mechanical and chemical attacks on the integrity of the goldfish skin using a pointed structure and a capsule of chemicals found at the front of the parasite. It is after they burrow into the skin that they grow their mouths.

Theronts can survive for a maximum of 4 days without finding a goldfish to feed on, and in most cases they will die after 2 days.

How long does it all take?

It all depends on water temperature. The warmer the water, the quicker the ick life cycle is complete. At a temperature of about 20 Celsius (70 Fahrenheit) the cycle would take up to 4 weeks. Raising the water temperature to 26 Celsius (80 Fahrenheit) would see the process complete in about a week.

As the optimum water temperature for goldfish is at the lower end of the scale, the ick life cycle will take much longer in a goldfish aquarium or pond.

Before going on to different fish species, it is worth repeating the fact that narrow-bodied and fat-bodied goldfish varieties should not be kept together.  The narrow-bodied goldfish such as common, comet and shubunkin will have eaten all the food before the fat-bodied ones (most fancy goldfish) realise it’s feeding time.

Also, before introducing any new tank mates, make sure to quarantine them properly beforehand.  Non-goldfish tankmates for goldfish have the potential to cause enough problems already without disease being one of them.

Another thing to be aware of - if the other species of fish can fit into a goldfish’s mouth, it will end up in a goldfish’s mouth.

Hillstream Loach

The hillstream loach is perfectly adapted for latching onto a surface and facing into a strong current.  Their natural habitat is fast-flowing streams, and they have a perfectly streamlined body.  Their perfect tank environment has a strong pump creating a current.  Because of this it is impossible to keep both goldfish and hillstream loaches in their ideal conditions.  Goldfish are not built to deal with a constantly strong current.

Like all algae eaters, they need to be fed away from the goldfish.  The best plan is to feed the goldfish at one end of the tank, then drop in some sinking food for the loach at the other end.  A varied diet is best for them, but algae tablets and sinking pellets should form the basis of their diet.

One nice feature of the hillstream loach is its ability to change colour according to its surroundings.

Weather Loach aka Dojo

The weather loach is a slender, fast fish that can grow up to 6 inches long.  They scavenge around the bottom of the tank, and thrive where there is fine gravel to root around in.

They can dart extremely quickly and have been known to leap out of goldfish tanks.  Obviously this is fatal if not witnessed.  It is a good idea to have some sort of cover over the water to prevent this, and only to uncover as much of the surface as is necessary when performing any aquarium maintenance.

When weather loaches are not sitting at the bottom of the tank, they do enjoy swimming in and around tank ornaments.  These ornaments can cause injury to fancy goldfish that have protruding eyes.

Corys

Corys are a type of catfish, and there are over 10 common cory species.  They usually sit close to the bottom of the tank, not doing very much.  Occasionally they will go for a swim, but will usually sit about doing very little.

Most cory species sold for goldfish tanks are not the type of catfish that can grow bigger than a man.  In fact they will not usually grow beyond 3 inches.

Like loaches they are bottom feeders, and need sinking food chopped up small.  They generally get on well with goldfish, but if not fed properly will suck the protective slime coat off goldfish.  This is a disaster if it happens.  The slime coat protects against all manner of goldfish illnesses and diseases, and its loss can be catastrophic for goldfish.

White Cloud Minnows

White cloud minnows are small fish that grow to about 1 inch long.  They are social fish and should be kept in shoals rather than as individual fish.  This feature makes them an attractive addition to an aquarium.

They will eat the same food as goldfish, and do not need fed separately as they can swim fast and can compete.

One thing they do like is a hiding place somewhere in the tank.

The main problem with white cloud minnows is their size.  When goldfish grow big enough, they will almost certainly eat them.

Other

There is one other species of fish that is often said to compatible with goldfish - the chinese algae eater.  However, it is a tropical fish and although it has been kept with goldfish with moderate success, it is not recommended.

The only other species that can be kept with goldfish are snails.  The most attractive one (subjective of course) is probably the golden apple snail.

With so many different types of filter available - each with very persuasive marketing all over the packaging - it is hard to know which is the right one for any given goldfish tank.

How Filtration Works

Mechanical filtration - this is simply the process of making water pass through a substance that will stop particles of dirt, faeces, uneaten food and other solid matter that are carried in the water. Examples of mechanical filtration include mesh, netting, sponge and filter wool.

Biological filtration - this is the process of turning poisonous ammonia (a by-product of decaying plants, food and goldfish faeces) into less harmful nitrates. These nitrates are then removed by regular water changes. Biological filtration is performed by bacteria that colonize the large surface area provided by sponges, gravel and filter wool. These bacteria can also be present in specific plant roots. Sometimes the mechanical filter and the biological filter are contained in the same physical item - e.g. a sponge - and sometimes they are two separate entities i.e. the water passes through a mechanical filter, then a biological one. Biological filters should only be cleaned in tank water, never in running tap water.

Chemical filtration - this form of filtration is used to remove chemicals from the water that are dissolved rather than suspended in the water, and that cannot be broken down by bacteria normally found in goldfish water. The most popular form of chemical filtration is activated carbon, that removes a number of toxic chemicals from the water, and is often used after adding medicinal chemicals to water. Another example is ammonia remover. Although biological filtration usually deals with ammonia, sudden increases in ammonia can overwhelm a biological filter.

Types of Filter

There are several different types of filter available, each with its own advantages and disadvantages. The following list summarizes the most common types.

Box filter - a very cheap, small plastic box that sits in the back corner of an aquarium, and is filled with filter wool and/or activated carbon. This type of filter is only suitable for very small tanks with very few goldfish in them, or in spawning tanks. It can also be used in larger tanks for quick and easy chemical filtration if it is filled with activated carbon.

Under gravel filter - a tray the same size as the bottom of the goldfish tank with one or two upright tubes attached to the back corners. It needs to be covered with gravel, because it is the gravel that acts as a mechanical filter, and provides the surface area for the ammonia-nitrite-nitrate bacteria to colonize. An under gravel filter is also cheap, but it is not very efficient and causes problems for aquarium plants.

Internal power filter - a two part filter consisting of a pump and a chamber containing a sponge. The sponge acts as both mechanical and biological filter. It provides good circulation and oxygenation of the water, and the sponge makes a very happy home for biological filter bacteria. However, the surface area is relatively small, so it can’t be used in large tanks. Also the filter itself may be a bit unsightly in the tank.

External power filter - works the same way as an internal power filter but sits outside the goldfish tank, often hanging from the top edge of the back of the tank. It is a popular choice for small aquarium owners as it gives the inside of the tank a more natural look, but it has the same limitations as an internal power filter.

Canister filter - this is a large external canister that works well in large aquariums. Most canister filters come with mechanical, biological and chemical filtration as standard. They work extremely well and hold a lot of filter medium, so don’t need cleaned very often. They are however for the more serious goldfish enthusiast, and this is reflected in the price. Also, they are not small and need room. This will often mean a custom-built cabinet to hide the canister.

Diatom filter - used for one off cleaning of the water, a diatom filter is a mechanical filter with a microscopically fine filter medium that can filter out almost all physical impurities in the water, right down to micro-organisms. A diatom filter cannot be used continuously, the medium clogs up too quickly. It is used at regular intervals to keep the water crystal clear.

Wet/dry filter - more likely to be found in large saltwater aquariums than goldfish aquariums, wet/dry filters work like sewage treatment beds. Water is trickled or sprayed onto a mechanical filter medium which provides high levels of oxygenation. It then passes on to the biological filter, and possibly a chemical filter. This type of filter is the most expensive and requires the installation of plumbing.

Summary

For most goldfish owners an internal power filter or an external power filter will do very well, with a box filter on hand for chemical filtering when needed. However, it is important to choose filters that will put enough water through to actually keep the water clean. At least 4 times the volume of the aquarium per hour, and more if the tank is heavily stocked.

Also, test the aquarium water regularly to make sure ammonia and nitrite levels are not rising. If they are, it could be a sign that biological filtering is not coping. If the water is cloudy or dirty, then the mechanical filter needs upgraded.

The reasons for goldfish losing their appetite fall into two main categories: goldfish diseases and environmental stress.

Goldfish Diseases

Constipation causes loss of appetite in goldfish. As regular readers of this blog will know from Goldfish Diet and Nutrition, goldfish do not have a stomach for holding and digesting food. Instead food passes through a goldfish’s digestive tract without stopping. If there is a blockage at one end there is no buffer zone to absorb the impact of food coming in at the other end, so feeding will stop.

A goldfish suffering from goldfish ick can also lose its appetite. Although not a guaranteed symptom of goldfish ick, it can occur in more advance cases of the illness and is due to a general and deeply unwell feeling caused by a goldfish disease that can eventually be fatal.

There is one more disease that can cause a loss of appetite in goldfish, but it is very rare among them. It is known as Hole in the Head Disease, or Freshwater Head and Lateral Line Erosion. More common among other types of freshwater fish it is a dangerous, but treatable condition that can be a cause of loss of appetite.

Environmental Stress

A change in diet can cause goldfish to go off their food. Obviously this is one of the easiest causes of appetite loss among goldfish to identify. If goldfish are changed onto a healthy diet from a poor one, they may well not eat for a few days. Their reticence to eat is due to being used to the old diet, and the slight stress of the change that may worry them until they get used to the new food.

Another environmental factor that may cause goldfish to lose their appetite is temperature variations. Again, regular readers of this blog will know from Preparing a Goldfish Pond for Winter that the natural seasonal drop in temperature can result in goldfish going the whole Winter without food. In parts of the world where Summer temperatures can fall sharply, pond goldfish can lose their appetite as a result.

Changes in water quality can also cause goldfish to stop eating, especially pH levels outside the optimum range. Goldfish that are put into new tanks that have abnormally high levels of ammonia and nitrite will also be susceptible to appetite loss.

Introducing goldfish into a new environment e.g. a new aquarium or pond, or bringing them back from the pet shop may well lose their appetite simply because of the stress of the move.

Finally, goldfish that see a new face pressed against the aquarium glass at feeding time, or goldfish that have to suffer a child splashing the surface of the water or tapping the aquarium glass will be frightened out of feeding. The same goes for pond goldfish that fear predation by a cat or heron. They simply will not surface for food, and will not emerge from hiding.

In Chinese there are two words that are spelt in English as yú. To the untrained ear they sound exactly the same, but one means fish and the other means bounty or surplus.

Therefore goldfish became a symbol of surplus and wealth, and a gift of goldfish is a blessing in the hope of good fortune.

The association of goldfish with good fortune is reinforced in legend. One tells of a period of drought ending when the world’s first goldfish jumped out of a well. Other chinese myths have goldfish present at the beginning of time.

In art, paintings of fish have been found on Chinese artifacts dating from around 8,000 BC, and goldfish can be found in Chinese art to this day. Not only do these images represent or bring abundance and success, goldfish represent the notion that it is possible for anybody to achieve whatever they want.

Chinese brush paintings of goldfish perfectly capture the lightness of the fins, the lines of the body, and the life-force of the animal in a few simple strokes.

In Feng Shui, a painting of goldfish is regarded as having the same effect as an actual goldfish tank by practitioners.

So for at least 1,000 years goldfish have been part of one the most ancient, mysterious, fascinating and successful cultures on earth. No wonder they are such a welcome feature in homes and businesses throughout the world.

There are 4 main aspects of water quality to test, all related to each other chemically.

Ammonia and Nitrite

Ammonia and nitrite levels can build up to dangerous or even fatal levels in a new tank. Ammonia is present in goldfish faeces, and is produced by rotting plant material and uneaten food. Certain types of bacteria feed on ammonia, turning it into nitrite, then nitrates. Until these bacteria are present in sufficient numbers, the ammonia and nitrite levels will rise.

The ideal levels of ammonia and nitrite are zero, but small amounts (less than 4 parts per million) can be tolerable. However, in a new tank with no ammonia-feeding bacteria the ammonia level will peak after a week, with the nitrite levels peaking a fortnight later. It is very important to have chemicals to deal with these toxins at hand during the first month of the aquarium.

Nitrate

As mentioned earlier, nitrites are eventually converted to nitrates, which are much less toxic to goldfish. Nitrates are still dangerous, and although goldfish that have been in the aquarium for a long time can build up tolerance, new goldfish will struggle to survive in water with high nitrate levels.

Regular, adequate water changes should be enough to prevent nitrates building up to dangerous levels. If testing shows high nitrate levels, either increase the frequency or the volume of water changes.

pH Level

pH is a measure of acidity and alkalinity. The scale runs from 0 (most acidic) to 14 (most alkaline) with 7 being neutral.

The optimum pH for goldfish water is slightly alkaline, but goldfish are happy with anything between 6 and 8. The most important thing to remember about pH management is that changes in pH are more harmful to goldfish that being outside the optimum range. Stable pH is the key.

Water Hardness

Water hardness is important because it regulates the pH of the water by a process known in chemistry as buffering. In practice it means substances dissolved in the aquarium water absorb the impact of changes that would otherwise change the pH of the water.

There are two measures of water hardness: general/total hardness and carbonate hardness. It is only necessary to measure one or the other, not both.

General/total hardness is often expressed as dH, GH or dGH. It should be at least 4dH to ensure buffering works, and goldfish can tolerate levels up to 20dH.

Carbonate hardness is expressed as mg/L and should be between 70mg/L and 400mg/L.

Testing Routine

Testing for ammonia and nitrites should - in theory - be unnecessary in an established goldfish aquarium. Testing for nitrates should be done with every water change, i.e. weekly. The same goes for pH and hardness tests.

The other time to perform testing is when something appears to be wrong: goldfish not eating, one dying, new fish dying and upon discovery of illness or disease.

It is also very important to record the results of testing. If there is an outbreak of chilodonella for example - which can be caused by poor water quality - it is no good knowing what the pH of the aquarium water is on the day of the outbreak if you can’t remember what it was in the days and weeks running up to the outbreak.

The comet goldfish has been around for over 100 years and has a slender body just like the common goldfish. What sets it apart is the long, flowing, deeply forked, pointed tail. In the official standard used for judging goldfish, the tail must be greater than three-quarters of the body length. One other notable feature of the comet goldfish is the single anal fin.

The comet goldfish can be red, red/white, orange, yellow, white or calico (red, white, orange, brown) in colour.

It is a hardy goldfish, and has no problem surviving in a goldfish pond over Winter. As it has a slender body it can swim fast, and therefore gets to food quickly. For this reason it has no problems keeping up with common goldfish, but should not be kept with slower fancy goldfish as it will leave them with nothing to eat.

One other thing to note about the comet goldfish - it can grow over a foot (30cm) long, so make sure there is plenty of room.

1. Change the goldfish diet to one with less protein and more carbohydrates. This will build up fat reserves in the goldfish, which will give them energy over Winter. If the water temperature drops below 10 Celsius, stop feeding them altogether.
2. Clean the pond. Remove all the organic material from the bottom of the pond (dead plant material and goldfish droppings). If possible remove the goldfish from the pond, drain all the water, clean the bottom of the pond, and replace the goldfish in clean water.
3. Cut away dead or dying leaves on plants. Some plants will require more severe pruning, so get appropriate advice from a good aquatic or garden centre.
4. If a biological filter is used, put new filter medium into it to maintain water quality all through the Winter.
5. If the goldfish pond is likely to have autumnal leaves falling into it, pin a fine mesh over the surface of the water to catch them. If they get into the water they will fall to the bottom and the decomposition will remove oxygen from the water, and thereby from the goldfish.
6. Put a hiding place for the goldfish in the pond. Winter is tough on the animals that eat goldfish too, and they will take an easy meal if they see one. An upside-down flowerpot or overhang arrangement will work.
7. If ice forms on the surface of the water, melt a hole in it. This allows oxygen to enter the pond, and carbon dioxide (and other toxic gases) to escape.

The Names of the Fins

a. Pectoral

b. Pelvic

c. Anal

d. Caudal

e. Dorsal

Stability

Goldfish move in 3 dimensions, therefore have 3 directions they need to maintain stability in.

Firstly, imagine a model goldfish with a rod running through it from the mouth to the tail, with the model spinning around the rod. Goldfish use their anal, caudal and dorsal fins to prevent this movement.

Secondly, imagine the rod is running through the model from top to bottom i.e. from the dorsal fin to between the pelvic fins. The movement on this axis is also controlled using the anal, caudal and dorsal fins.

Finally, imagine the rod is going through the model from side to side, producing movement that makes the head and tail go up and down. Goldfish use their pectoral and pelvic fins to control this movement.

Direction & Steering

Goldfish move their caudal fin from side to side for forward propulsion. The pectoral fins are used for more delicate movement, both forwards and backwards.

Goldfish steer with their pectoral fins, and also use the dorsal fin when turning sharply.

In the wild, goldfish feed on algae, plants, plant roots, worms, insects, larvae, tadpoles, small fish, snails and anything else they can fit in their mouths to taste and check if it’s ok to eat.

Although aquarium and pond goldfish are not wild and look nothing like wild goldfish, they have exactly the same digestive tract, and need the same sort of diet.

Feeding them flakes from a tin twice a day is not the way to do it.

Mealtimes

As stated above, it is best to try to mimic what goldfish would experience in the wild. As they would be almost constantly grazing, small meals are better than large meals. If goldfish are given a lot of food one or two times a day, they will pass most of it undigested. Goldfish do not have a stomach to hold food in while it is broken down, it just keeps on moving.

Dried Flakes, Pellets and Tablets

These types of goldfish food should be used as a base in their diet, but not as the only source of nutrition. The better ones will provide fibre, vitamins and minerals - as well as some quality protein, but they will not provide a varied diet.

Also, beware of flakes that are bulked up with cheap corn starch, or use cheaper vegetable proteins instead of fish proteins.

Another point worth noting is that dried foods swell up when they get wet. If they swell inside a goldfish, they may cause the swim bladder to be pressed out of shape, causing problems for the goldfish.

Frozen and Freeze Dried Food

These types of food are high in nutritional value, and there is plenty of variety. They are high in protein and contain all the amino acids that goldfish need for healthy muscles and tissue.

Freeze dried foods also need to be pre-soaked because, like dried food, they swell up when they get wet.

Live Food

Live food such as daphnia, freshwater shrimp and midge larvae is the most nutritional of all for goldfish. However there are a number of problems associated with giving live food to goldfish.

Firstly it is much more likely than any other goldfish food to carry disease or cause illness.

If worms or larvae are harvested from the wild, it is vital to ensure they do not come from ground that has been exposed to pesticide.

Secondly, they are harder to obtain than other types of goldfish food, and it is often necessary to breed them in separate tanks.

Finally some species of worm can disappear into gravel and set up home in an aquarium, causing problems for the goldfish and the aquarium.

Fruit and Vegetables

Certain aquatic plants can be grown in separate tanks and fed to goldfish, and they also enjoy a wide range of fruit and vegetables.

Make sure hard vegetables like carrots are cooked or finely grated, citrus fruit sections have the skin removed, things like peas and grapes are peeled, and softer items like lettuce and apple are chopped up. Fruit that is made of small constituent parts like raspberries can be dropped in whole, and the goldfish will pull the smaller manageable parts off.

One word of warning about fruit and vegetable - use them as treats and nibbles, not as a major part of a goldfish diet.