The best method is to use two containers: one for disinfecting, the other for rinsing.

The best active ingredient to use in the disinfecting container is formaldehyde, which is available from fish and aquarium shops, and online.

The normal concentration of shop bought aquarium formaldehyde is 37%.  Adding 2 tablespoons of this to a medium-sized bucket will be enough to kill bacteria and parasites.

Simply dip the net, scraper or whatever into the formaldehyde solution, then into the rinsing container which contains nothing but clean water.  There is no harm in storing the equipment in the disinfecting container either.

A good tip is to add a small amount of dye to the disinfecting container.  Not only will this easily distinguish the otherwise colourless disinfectant from the rinsing water, it will also give an indication as to when the rinsing water needs changed as it gradually gets the colour of the dye.

The problem is that the water inside the ornament does not circulate.  This means it is low in oxygen and high in bacteria.  In other words it is stagnant, and the ornament has become a disease factory.

Bacteria escape and enter the main body of water, making fish sick and killing them.  Without knowing what is causing the problem, an otherwise diligent fishkeeper can end up very frustrated trying to find out the cause of the infections.

Thankfully there is an easy solution that doesn’t mean removing every hollow ornament.  The silicone sealant that is used to hold aquarium glass together can be injected into the eye sockets of a fake skull, the opening of a sea shell, the windows and doors on model houses, and so on.

This means that the ornaments are no longer hollow (even though they look it), and interesting or themed aquariums don’t need to lose their character to be safe for fish.

Fantails are more common in the far east than in Europe and North America, but they are becoming more popular due to their advantages over other fancy goldfish.

The body of a fantail is shorter and rounder than a common goldfish.  The tail and anal fins are split in two, with the tops of the tail fins closer together than the bottoms.  This gives the tail a triangle shape when viewed from the rear.

The most common colours for fantail goldfish are red and calico.

Not only can fantail goldfish tolerate low winter temperatures in ponds, they can swim fast enough to get their own share of the food when in the same water as fast goldfish.

Also, as they do not have head growths, eye bubbles or nasal growths, they are less prone to bacterial infection than other fancy goldfish.

However, in common with all goldfish that have mis-shapen bodies, they can suffer from swim bladder problems.

Overall, a nice addition to an aquarium that has room for an extra goldfish, without the hassle of making sure it is set up for fancy goldfish.

N.B. There are several goldfish varieties that are known as ‘fantail’ varieties, the bubble eye goldfish being one of them.  However the fantail goldfish discussed here is a variety in itself.  When used to describe a group of varieties, it refers to goldfish that have shorter bodies, short fins and a double forked tail.

Most aquatic snails are tropical and should not be kept with goldfish.  It is particularly worth noting that apple snails are often sold as ideal tankmates for goldfish.  They are not, for two reasons: one, they are tropical snails that prefer the water temperature to be about 4 degrees celsius warmer than is healthy for goldfish; and two, goldfish will eat the ends of their antennae and eye stalks.

There are only two snail species that can be kept with goldfish, and they are the ramshorn snail and the pond snail.

The ramshorn snail has a shell in a flat coil shape that can be bright red, pink, blue, black, green, brown, orange or yellow.  It can also have stripes or spots in combinations of these colours.  The red and pink ramshorn snails have actually got very low pigment levels, allowing their unusually (for a snail) red blood show through.

The pond snail’s shell is more like the shape of a twisted cone, broad at the opening and ending in a point.  The variety of colours is not as wide as the ramshorn, but it can have a range of patterns and light and dark colours.

The main benefit of aquarium snails is their appetite for algae.  They will clean the glass, stones, ornaments, pumps and anything that has a surface algae will grow on.  This saves a lot of time and effort, and generally means that weekly water changes don’t need to be accompanied by scraping the glass and siphoning off the scrapings.

One thing that is very important to snails is the pH level of the water.  pH is a measure of the acidity or alkalinity of the water.  Although goldfish are happy enough with anything between pH6 and pH8, snails need it to be over pH7.  Anything below pH7 is acidic and will erode snails’ shells.

The biggest problem with aquarium snails is their capacity for breeding.  For every snail in a tank at the start of a year, 500 can be expected at the end of the year.

The solution to such a problem in most animal species would be to get either two males or two females to prevent breeding.  This won’t work with aquarium snails because both ramshorn and pond snails are hermaphrodites.  This means that each and every one of them has both male and female reproductive organs, and is therefore able to mate with any other snail of the same species.

The obvious solution to this problem would be to keep only one snail.  Unfortunately that won’t work either.  Both the ramshorn and the pond snail have an ability known as auto-fertilisation.  This means single snails can produce offspring without a breeding partner.

If this happened in an aquarium, all snails would be exact clones of the parent that auto-fertilized.  This is obviously not ideal, but in the wild it is a technique used by snails to quickly stock a body of water that has no snails in it.  Other unrelated snails will most likely arrive to mix in some new genes and prevent genetic problems.  Both species of snail can survive out of water, and do so to get to new ponds and lakes.

Once food is in the goldfish’s mouth, it is pushed to the back of the throat where a set of teeth grind and crush it against a hard pad.  There is an excellent photograph of goldfish teeth here.

The ground down food then passes down a tube called the oesophagus (pronounced oss-SOF-a-gus), which squeezes out excess water.  The oesophagus is lined with taste buds, little muscular hairs that brush the food along, and cells that produce mucus to keep things moving on.

The oesophagus empties into an expandable section of the goldfish’s digestive tract that for many years was thought to be a stomach.  However it does not produce any acid or enzymes to distinguish it from any other part of the gut.  It is simply a buffer zone to hold excess food as required.

Just before this expanded section, chemicals from the gall bladder and pancreas are pumped in with the food.  The ones from the gall bladder make up bile, which is used to break down fats; the ones from the pancreas contain enzymes that are used to break down proteins.

All along the digestive tract are cells that secrete enzymes that act on carbohydrates, breaking them down into sugars.

From the expanded section to the goldfish’s anus, lots of mucus is produced and as much useful material as possible is absorbed into the bloodstream to be used for energy, growth, protection and repair.

The whole process takes about 16 hours at an ideal temperature, but will slow to a stop in ponds during cold periods.

This is the reason goldfish should not be fed when it is cold.  Any food they do ingest can end up rotting inside them.  Any they don’t ingest can end up rotting in the pond water.

The nature of the goldfish’s digestive system also illustrates why it is vital to feed small meals throughout the day, rather than one or two big meals.

The food eaten in big meals will not be in the goldfish long enough to be broken down properly.  Most of it will come out the back end before digestion has a chance to act on it.

Related article:

Goldfish diet and nutrition

Bubble eye goldfish are thought to originate in China a long, long time ago as the result of a mutation being bred into other forms of large-eyed goldfish.  One possible reason for such a mutation being encouraged is that in ancient China, goldfish were kept in jars (aquariums hadn’t been invented).  Therefore the only way to view the goldfish was from above.  This could also explain why, in common with other “fantail” goldfish, there is no dorsal fin, and a split tail fin.

Bubble eye goldfish are available in all the colours any other goldfish is available in: red, yellow, orange, brown, black, blue, white, silver or calico.  (For a full explanation of goldfish colouring see Goldfish Colouring Explained).

Naturally enough, all the major problems associated with bubble eye goldfish are because of the bubbles.

1. They can only see food that is above them.  There are a few ways to get round this problem.  Use slow-sinking food, clip fast-sinking food up the side of the tank, and always put food in the same location.  However, the best way to ensure bubble eye goldfish get proper nutrition is to train them to hand feed.

2. They are extremely poor swimmers.  Even relatively slow swimming goldfish varieties such as the black moor or oranda will beat a bubble eye to food every time.  They are so slow because the bubbles make the fish front-heavy, turning swimming into a real effort.  To make matters worse, the bubbles jiggle up and down, and left to right as the fish swims.  It’s like trying to keep one’s head still while walking with a large plastic bag full of water tied to each ear.  To top it all off, having no dorsal fin reduces stability even more.  As a result of all this, bubble eye goldfish will spend a lot of time resting on the bottom of the tank.  Older bubble eye goldfish will very often give up on swimming altogether, preferring to float around on the current provided by the pump.

3. The bubbles burst easily.  Sharp gravel, pointy plants, ornaments and filters/pumps all present a danger to the bubble eye goldfish’s bubbles.  Make sure there is nothing in the tank that can cause such an injury.  If a pump or filter intake is capable of snaring a bubble, it probably will.  Cover any such hazards with sponge.  If a bubble does get burst, it will likely grow back.  However, it will not be the same size and shape as the one on the other side.  There is also the risk of bacterial infection after a bursting incident.

4. Bad eyesight is widesread in bubble eye goldfish.  It isn’t great to start with, and will probably get worse.

As with all fancy goldfish, the bubble eye can be susceptible to swim bladder problems because of their more rounded body shape.

Overall, the bubble eye goldfish is a delicate fish that is definitely not for beginners.  However, they are happy when healthy and cared for, and although an aquarium will have to be stripped of many decorations that other goldfish can negotiate quite safely, bubble eye goldfish provide their own decoration in sparsely furnished tanks.

Parasite life cycle

The reasons behind the scarcity of black spot disease in aquariums can be found in the life cycle of the parasite that causes the disease.

The eggs fall into water in the droppings of birds that have eaten infected fish.  About a month later they hatch, and are called miricadia.  Think of them as little hairy egg-shapes that move the short hairs in unison to swim.

The miricadia swim until they encounter a snail, into which they burrow and develop.  About 6 weeks later, cercariae emerge.  These look like little tadpoles with forked tails, and their aim is to find a fish.

When they find a fish they burrow under the skin before losing their tails.  Now they are called metacercariae, and they protect themselves in the fish with a hard cyst that contains dark pigment.  These cysts appear as small black spots and give their name to the disease.

The next stage is for a bird to eat an infected fish, where it develops into a flatworm with a shape a bit like spoon with a broad handle.  Although the parasite feeds off snails and fish, it is on the bird that it places the greatest burden.

It is in the bird that they consume the resources necessary to reproduce and lay countless eggs which then fall into water in the bird’s faeces.

Barring highly exceptional and unlikely circumstances, the only way for parasitic black spot disease to get into an aquarium is when infected snails are introduced.

When it comes to ponds, however, the chances of infection are much higher.  Any visiting heron or kingfisher can cause and outbreak.

Effects on fish

Fish infected with parasitic black spot disease will usually display signs of iritation such as rubbing and flicking of the body.

The black spots themselves appear as small, dark, well defined, raised areas of skin about the size of a pin head.

Lasting damage is rare, although blindness can occur if the carcariae end up in the fish’s eye in large numbers.

Other than that, there is no cause for alarm when healthy adult fish are infected.  Young fish can be killed by the disproportionately high requirements of the parasite on their bodies, but the parasite will not complete a life cycle if it kills the fish.

It is worth noting at this point that on the rare occasion of aquarium fish becoming infected, the number of black spots on each fish will likely be huge.

This is because there is a high number of fish that are not eaten by birds.  So the flatworm needs to produce as many eggs as possible, in order to infect as many snails as possible, in order to get lots of fish, thus increasing the chance of an infected fish being eaten by a bird.

Miricadia on a snail that enters an aquarium will emerge to find they have no trouble finding a fish.  Not only that, they will all attack the same few fish.

Treatment

Other than removing snails, there is no other treatment necessary in an aquarium.  Providing the fish in the aquarium do not get eaten by a bird, and the same bird does not return to the aqarium a month later to deposit faeces in it, the parasite will die off.

In ponds on the other hand, it will probably be necessary to purchase treatment for the disease.  Copper sulphate can be used (only under licence in some parts of the world) to kill snails, and many commercial treatements are also available that target the parasite.

Although impossible to prevent, it is also wise to discourage herons and other fish-eating birds from visiting ponds.

Ammonia burn

Most examples of black spot disease in aquariums are the result of ammonia burn on the fish’s skin or fins.  When the affected areas start to heal, the small patches that recieved the harshest burn turn a dark brown or black colour.

The black spots themselves appear as discoloration of the skin, rather than something in or on the skin.  They can range in size from barely noticeable to a “rolled around in black paint” look, but are usually small smudges.

Blackened skin from ammonia burn is actually a good sign.  It means the ammonia has dropped back to a safe level, and the fish’s skin has started to heal.

However, it is a worrying sign that the ammonia level was raised in the first place.  Action needs to be taken to minimize the risk of raised ammonia.  A lot of fish that suffer ammonia burn don’t get the chance to get black patches on their skin.  They get killed instead.

Spot the signs

Fish in a tank or pond with high levels of ammonia will gasp for oxygen at the surface, float on their sides, sit at the bottom, lose their appetite, get red streaks in their fins, develop reddening around the gills, and/or make swimming look like hard work.

As soon as any of these behaviours are spotted, get the water tested to confirm ammonia poisoning and take action to remove it.

Removing ammonia

Changing the water is the best way to get rid of ammonia.  Do it every day until the ammonia levels are down to an acceptable level i.e. less than 4 parts per million.  An ideal level is less than 2 parts per million.

The other option is to use chemical treatment, but water changes are obviously better as they do not involve adding further chemicals to the water.

Prevention

Test the water regularly, and change it regularly.  High ammonia levels are a sign of a badly managed aquarium.

Do not overstock.  Too many fish produce too much waste, which contains ammonia.  If the filter can’t cope, ammonia poisoning is inevitable.

Do not overfeed.  Uneaten food decays, producing ammonia.

Use a treatment tank if the water needs to be medicated.  Medications for unrelated fish diseases can kill the bacteria in the filter that remove ammonia from the water.

Keep a very close eye on new tanks.  Ammonia poisoning occurs most often in new tanks.  Ammonia will peak at the end of the first week.  It is advisable to start with only one fish so waste is kept to a minimum.

Related articles

Choosing and Aquarium Filter

Goldfish Aquarium Water Testing

Changing the Aquarium Water

Interesting stuff.

Forebrain

At the front are the smell detectors, technically known as the olfactory lobes.  They are directly connected to the fish’s nostrils by the olfactory nerves.  The information processed in the olfactory lobes is passed to the telencephalon, which “understand” what the smells are.

Together the olfactory bulbs and the telencephalon are known as the forebrain.

Research has also indicated that the forebrain may play a part in learning and retaining automatic responses to things that are unpleasant, and also in spatial awareness.  One experiment found that goldfish with damaged forebrains were less successful at memorizing a maze.

Finally, some fish make noises, and this is also thought to be controlled by the forebrain.

Midbrain

The midbrain (aka mesencephalon) sits directly behind, and is connected to the forebrain.  It’s main purpose is to process and understand the signals sent from the fish’s eyes to the brain.  It is responsible for sight.  In fish that hunt by sight, this part of the brain is comparatively larger.

Other functions of the midbrain include learning and controlling muscular reactions.

Fish are also thought to be able to tell what direction a sound comes from by using the midbrain.  (Fish have bones in the skull that form an inner ear).

Hindbrain

The hindbrain (aka metencephalon) is mostly responsible for controlling swimming, including the actions of the swim bladder.  It decides how much work a muscle does, how fast it works, and works out the balance of the fish.  Overall, the hindbrain controls what direction the fish swims.

Although the hindbrain is the largest part of the brain in most fish, those that swim fast and hard have the largest of all.  Fish that spend most of their lives latched on to rocks or other fish don’t have a large hindbrain.

Another function of the hindbrain is to detect chemicals that have an effect on blood sugar levels.

Other

There are several other smaller structures in the fish brain that control functions relating to hormones, breathing, salt intake, signals from the lateral line and reacting to all the other organs in the fish, and stimuli it will encounter.

Preparation

Affected goldfish need to be removed from the tank and put into a treatment tank.  (Some people refer to a treatment tank as a hospital tank, isolation tank or quarantine tank.  These names are interchangeable.)

Any small tank fitted with a box filter and containing no ornaments or plants is suitable as a treatment tank.

The reasons for isolating the affected fish are:

• to help prevent the spread of secondary infections to other fish in the aquarium
• because one of the treatments is an antibiotic that will either wipe out or decimate the good bacteria population on biological filters
• it’s easier to keep treatment tank water in tip-top condition
• there is reduced (zero if it’s only one fish) chance of fighting or bullying causing further problems

The only other thing to do before commencing treatment is to raise the water temperature a couple of degrees in the treatment tank.  The bacteria that cause tail and fin rot prefer cooler water.

Treatment

There are two separate parts to successfully treating tail and fin rot: one is to treat the main tank, the other is to treat the affected goldfish in the treatment tank.

To treat the main tank, change the water, test the water quality and make any improvements that are necessary, and make sure the goldfish are receiving a healthy, balanced, nutritious diet.  Also make sure there is no rotting plant or food material in the gravel at the bottom of the aquarium.

To treat the affected goldfish, put a teaspoon of aquarium salt in for every gallon of water in the treatment tank.  Salt is a natural antiseptic and has wound-healing properties.

The other treatment, as already mentioned is antibiotic.  The most common ones used to treat the bacteria behind tail and fin rot are tetracycline, chloramphenicol and oxytetracycline.  Dosing instructions will be provided with the antiboitics, most of which come as commercial brands with user-friendly labels.

Obviously most treatment tanks are small, and some of the dosing instructions may be for larger quantities of water.  A handy tip is to pour 10 spoonfuls of water into a container, then add the antibiotic as stated on the label.  To dose the smaller quantity of water in the treatment tank, just use the same spoon to dole out 10ths of the large dose of antibiotic, until the correct amount is in the treatment tank.

One other handy tip is to completely ignore the length of treatment stated on the label.  Continue the treatment until tail and fin re-growth is noticeable.  Stopping treatment before this may mean the bacteria have been knocked down, but not finished off.

One proviso is that if the treatment has gone on for 3 times the length stated on the label, it is probably not working.  When this happens, change to a different treatment.

At all times, make sure the water quality in the treatment tank is what is should be.

Prevention

No secrets here.  Keep the water quality good, feed a healthy balanced diet, don’t overfeed, don’t have too many fish in the tank, keep the temperature steady, quarantine new goldfish, and make sure all the goldfish in the aquarium lead a stress-free life.

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.