Keeping Goldfish

[naiad]

Goldfish expert reporting for duty.

Originally Posted by wet

I don't quite understand what they mean, polarized vision used by goldfish to hunt? I thought goldfish were primarily vegetarians (grass carp?)

I thought polarized vision didn't work under water, only above water looking through the reflection.

Goldfish will eat a wide range of foods, including algae, plants, invertebrates, fish eggs and small fish.

Many books and websites say that the goldfish is a domesticated form of the carp. This is incorrect. They are different species, and both have been domesticated separately. Some goldfish and carp may look almost identical, but the carp (Cyprinus carpio) grows much larger and has barbels, unlike the goldfish (Carassius auratus).

The grass carp is yet another species, with the impressive Latin name of Ctenopharyngodon idella. It feeds mostly on plants and algae.

I don't know how polarized vision would help them, maybe to see insects which have landed on the surface, or to spot predators above the surface?

Although the goldfish and carp are mostly bottom-feeders, some related fish are surface and midwater feeders, such as the Orfe. If they also have polarized vision, they may benefit more from it. They hunt mostly by sight, and feed on plankton, surface insects and small fish. The goldfish and carp use a combination of sight, smell and random 'vacuum-cleaning'.

Originally Posted by Pastor

I have seen goldfish eating their young in the fish pond. Lucia?

They will often eat their eggs and young if given the chance. Once the young are past the transparent fry stage and look like small fish, they are less likely to be eaten. In a pond with lots of plants and other hiding places, some will survive. It is often better that only a few survive, as they produce thousands of eggs, and overcrowding will produce stunted fish.

On the subject of grass carp, they are often sold for algae control. They do eat blanketweed algae in the wild, but in captivity they will eat almost anything else to avoid it. If given a choice of foods, they prefer to eat commercial carp food, invertebrates and small fish. If these are not available they will turn to plants, eating first the leafy ones and then the tough ones such as waterlily stems. Only if none of these is available will they start to eat the blanketweed. It must taste as bad as it looks.

[naiad]

Originally Posted by BatRay

In general, animals have a much wider range of color vision than humans. That makes me feel cheated.

The goldfish is a masterpiece of nature. It has many abilities which could come in useful, and it doesn't have a 3 second memory. Maybe being a goldfish is not so bad.

- It can see a full range of colours, unlike many other vertebrates and most mammals. It also has a very large field of vision, including above the surface.

- It can navigate in the dark by using its lateral line to detect objects.

- It can clone itself - some populations of wild goldfish are all-female and produce identical female offspring.

- Its hypoxic tolerance is very high, so it can live in stagnant water. It is closely related to the crucian carp.

- Unlike most animals, goldfish and some other coldwater fish can function normally with a wide range of body temperatures. I have seen them still reasonably active at 3c and 30c.

- There are more breeds of goldfish than any other fish, and it is thought to be the first to be domesticated. I don't envy them for that, as features include raspberry-like head growths and protruding eyes.

- The ones in pet shops and fairgrounds are not fully grown - they can easily reach 20cm and 1lb, and sometimes a lot more.

- They have 8 teeth, which can only be used for chewing and not biting. The teeth are replaced as they wear out.

- The goldfish is not meant to be orange. Despite its common and latin names describing it as golden, it was originally bronze or brown. Orange ones were specially bred. They are supposed to be unable to survive in the wild, but probably because of the above reasons, they seem to manage very well despite their colour.

[BatRay]

I've had some that stayed brown for a long time, then slowly changed to orange. Usually, the brown concentrates and recedes until it is limited to the tips of the fins and a very funny moustache. That goes away too. Mine also grow quite large. I recently lost a fantail whose body was larger than a golf ball. It was a very sad loss.

Say, Lucia, would you happen to know if goldfish can get bubbles in their fins? Mine seem to have that problem.

[naiad]

Most goldfish start off brown. They may change colour after a few weeks or several years. Some remain brown for the rest of their life.

Sorry about your fantail. I lost a beautiful Calico Lionhead a few months ago.

I now have 10 goldfish. 9 of them were unwanted pets, probably because they have grown too big. Some are still growing, I don't know what to do!

They can get bubbles in their fins. I explained how that happens here. If the excess plants or algae are removed, the bubbles should disappear soon. Are your fish indoors or outdoors?

[BatRay]

They are indoor fish. Their tank became quite dirty awhile back, but I did a 90% water change and fixed it. Their tank does not have any plants, but it does seem to have algae overgrowth. I'm thinking about switching them to a tank with less algae, and switching my pleco to the algae-filled tank. That sound ok?

[naiad]

It is hard to tell without seeing it, but if there is not a huge amount of algae and the fish are doing well, maybe better to leave them where they are. Mine are outdoors, with lots of algae. I change a bit of water every day in the summer to remove some of the green algae in the water. Some green and brown algae grow on the sides of the tub, but these keep the water clean, and the fish also have fun eating them. There are suction marks where the fish have eaten the algae.

Putting the pleco in the tank for a while may solve the problem, if the temperature is over 20c and the pleco is not disturbing the goldfish.

It is hard to get a goldfish tank to work properly. They produce a lot of waste and often the water quality is very poor, causing disease problems. This is partly because they are big and active, and partly because unlike many other fish, they chew their food. This releases food particles and nutrients into the water, feeding algae or bacteria. The algae eat the nutrients and keep the water reasonably clean.

That is why I leave some algae. Although they don't look great, they keep the water clean.

[wet]

Originally Posted by naiad

It is hard to get a goldfish tank to work properly. They produce a lot of waste and often the water quality is very poor, causing disease problems. This is partly because they are big and active, and partly because unlike many other fish, they chew their food. This releases food particles and nutrients into the water, feeding algae or bacteria. The algae eat the nutrients and keep the water reasonably clean.

Goldfish seem to have many amphibious qualities. Chewing is not common in fish (water) or birds (aerial) or most amphibians or snakes. Some frogs have psuedo-teeth they chew with.

Do goldfish have unusual fin bones, perhaps vestigial lobe fins that returned to more ray-like fins?

[naiad]

Quite a lot of fish chew their food. The ones that I know of are the carp, cichlids, catfish and loaches. These are all freshwater, and are huge families which include most freshwater fish species. They have teeth on the pharyngeal bones. Some also have teeth in the front of the mouth, such as many catfish species and cichlids.

Although they may survive for a long time out of water in damp conditions, the goldfish and carp never leave the water voluntarily and are not adapted to move on land. Their fins have weak rays which will not support their weight. I am not sure whether they are able to absorb oxygen from the air with their swim bladder in emergencies. They can certainly empty and fill it through the mouth. When a goldfish is stressed it will sometimes expel air from its mouth with a 'popping' sound and sink to the bottom. When the danger is past it will gulp air at the surface to regain buoyancy. Newts and salamanders will empty their lungs, often with a squeak, when disturbed, to escape danger by sinking.

Most aquatic animals, including most fish, produce ammonia as a waste product, excreting it through their gills. Mammals produce urea and excrete it through their kidneys. Urea is far less toxic and so does not need to be immediately excreted and diluted. The goldfish is one of a few species which can change from producing ammonia to urea if the ammonia concentration in the water is becoming dangerous. Any fish species which leaves the water must take this step.

The loaches and catfish, which are related to the carp family, often leave the water. Most of them can breathe air, by intestinal respiration or modified gills. Some, such as the weather loach, are long and thin, and move like snakes on land, without using their fins much. Others 'walk' on strong fin rays. Plecos and Corydoras do not leave the water often, but they can stand on their fins, and I have seen small plecos 'walking' underwater on a sandy substrate, using their strong and spiny fins with a movement like a salamander.

Many amphibious species, such as Weather Loaches, Walking Catfish and Climbing Perch will leave the water in wet weather to find new ponds with food and potential mates. This is often triggered by low barometric pressure (which predicts rain), and captive ones may escape their tank. If they are able to, Walking Catfish will climb into a neighbouring tank or pond and eat the occupants.

[wet]

Right, I was thinking of the marine fishes not chewing much, but freshwater fishes chewing due to having more amphibious ancestors at some time, and so having been selected via survival in drier climates, where suction feeding doesn't work outside of water. Their chewing muscles and tongue are probably less well developed than terrestrial chewing animals, but much better than ocean fish.

Others 'walk' on strong fin rays. Plecos and Corydoras do not leave the water often, but they can stand on their fins, and I have seen small plecos 'walking' underwater on a sandy substrate, using their strong and spiny fins with a movement like a salamander.

Do these fin walkers move their fins out laterally to the sides and paddle (like oars) in very shallow water? Or is the walking limited to nonshallows?

I think all these freshwater must have had lobe fins which since disappeared, or developed a eel-like crawl, or directional flipping, in the past, and this selected for better air breathing as a result.

I guess polarized vision might also be selected for under those conditions.

[BatRay]

I have weather loaches as well, and they seem to get along with the goldfish. My two goldfish are in a ten-gallon aquarium, and I have had no end of problems with getting a lid for it, keeping the lid in good shape, leaks, and just about everything else. You are right, though. They do seem to be sucking the algae off the sides. I just wonder if they don't have enough space. They're both pretty good-sized fish.

[naiad]

Originally Posted by wet

Right, I was thinking of the marine fishes not chewing much, but freshwater fishes chewing due to having more amphibious ancestors at some time, and so having been selected via survival in drier climates, where suction feeding doesn't work outside of water. Their chewing muscles and tongue are probably less well developed than terrestrial chewing animals, but much better than ocean fish.

Do these fin walkers move their fins out laterally to the sides and paddle (like oars) in very shallow water? Or is the walking limited to nonshallows?

I think all these freshwater must have had lobe fins which since disappeared, or developed a eel-like crawl, or directional flipping, in the past, and this selected for better air breathing as a result.

I guess polarized vision might also be selected for under those conditions.

Probably the modern bony fishes and amphibians both descended from a species like the lungfish.
Image:Australian-Lungfish.jpg - Wikipedia, the free encyclopedia
The several types of lungfish have lobed fins, heavy scales, and both lungs and gills. They can survive for months out of water, encased in mud with a breathing hole. They have powerful jaws and are ambush predators, grabbing and crushing their prey of large invertebrates, small fish and amphibians. Despite their lungs, they are very negatively buoyant and spend most of their time resting on the bottom. They breed in a similar way to amphibians. The eggs are gelatinous like frogspawn, and they hatch into 'tadpoles' with external gills. The male looks after them.

Some of them may have gone on to become fully aquatic. They developed an advanced swim bladder for neutral buoyancy, and lighter scales. The gills became well-developed, so using the swim bladder as a lung became unnecessary. The fins became lighter and the long tail developed into separate dorsal, caudal and anal fins. Heavy jaws became a lighter protrusible mouth for suction feeding. These types of fish gave rise to the modern bony fishes, of which the carp, tetras, etc. are the most advanced group.

Other primitive lungfish species took a different path. They lost their internal gills, and the lungs became well-developed. The fins became stronger and could support its weight on land. The tail fin was lost, or lost its rays and became a decorative 'crest'. The scales were lost because of their weight, and were replaced with moist skin. The jaws became lighter but were still used for grabbing prey. These became the amphibians.

The fin walkers use their fins only to grip the surface they are walking on. The fins are not actually moved, they are pushed into the sand as the body is curved from side to side, like a salamander walking.

Some plecos move their pelvic fins (equivalent to hind legs) up and down alternately, like someone swimming with bi-fins. This is not used for forward movement, at least in modern species. They do this while stationary with their sucker-mouth attached to a surface. The fin movement creates a backward current of water, which is directed onto their eggs or young to provide oxygen and remove sand or mud.

[naiad]

Originally Posted by BatRay

I have weather loaches as well, and they seem to get along with the goldfish. My two goldfish are in a ten-gallon aquarium, and I have had no end of problems with getting a lid for it, keeping the lid in good shape, leaks, and just about everything else. You are right, though. They do seem to be sucking the algae off the sides. I just wonder if they don't have enough space. They're both pretty good-sized fish.

They are probably getting big for the tank. Two big goldfish and two weather loaches in a 10 gallon aquarium is a lot. A bigger tank would be better for all of them.

Make sure it has a well-fitting lid, as the weather loaches often try to escape.

Originally Posted by sanso

This sounds like there's lots of info for fish-keepers here. Do You think it'd be worth a thread of its own? (I'm serious, I have no clue of aquarium stuff. Maybe You're just exchanging commonplaces..)

Yes, that would be a good idea.

[sanso]

Hey everyone,

because of the quality of the goldfish-topic, I moved some of the goldfish-related posts into their own thread here - which they clearly deserve.

Keep it up! Excellent stuff!!

[foxfish]

Originally Posted by BatRay

I have weather loaches as well, and they seem to get along with the goldfish. My two goldfish are in a ten-gallon aquarium, and I have had no end of problems with getting a lid for it, keeping the lid in good shape, leaks, and just about everything else. You are right, though. They do seem to be sucking the algae off the sides. I just wonder if they don't have enough space. They're both pretty good-sized fish.

It would be difficult to offer your pets a home that was too big for them!
There may be exceptions to the rule & obviously limitations to ones own environment but -
Goldfish or any captive fish will need special attention to maintain a healthy environment, that is, if you care for their health & longevity.
Keeping pet fish can be very simple if you understand jut a few basics.
(1) A large volume of water is far more stable than a small volume of water IE if you were to add one drop of food colouring to glass of water you would see a colour change, one drop of food colouring to a 100 gal tank would not be visible at all! Now apply this logic to a fishes poo!
(2) Although water changes are very important in the majority of tanks the quality of water you use is equally important. Very often tap water contains many chemicals that will either harm your fish or more likely kill friendly bacteria that is the life line to your fishes health.
(3) Filtration, you could use the same rule of thumb as no (1) big is best but even a basic biological filter is better than not having one! However there is little point in trying to maintain a bio filter if you dont understand how they work?
In summery, keeping a pet fish in a healthy environment & being able to understand some very basic chemistry will give you long term enjoyment in preference to watching a dying fish while you accidentally, slowly kill it!
Of course there are people who have successfully kept fish with little or no understanding of their real needs but take a look at someones tank who does! Goldfish can live for a very long time in ideal conditions, normally in a outdoor pond but a beautifully planted filtered & maintained tank is a joy to own.

[naiad]

Sanso, thanks for the new thread.
Foxfish, good advice.

I am trying to sort out proper housing for mine. In the spring they will need a pond filter, because with so many of them water quality will become an issue in warm weather. They are also growing constantly, competing for the title of biggest fish. I suspect that the carp hybrid will eventually win.

They can still be a mystery - after 20 years of keeping fish they still do things I don't understand. Recently the weather started to become very cold, and I did not want to risk the two smallest fish, the carp hybrid and a goldfish with very long fins. I brought them indoors, and set up a plastic tub with a filter. At first they were happy, but soon they became extremely stressed. The water quality seemed good, and they had no obvious disease, but they rested in a corner or in a plant pot most of the time. If they were disturbed by someone walking past, they started dashing around and hitting their noses on objects. Eventually the carp stopped eating, and I decided that the only thing I could do is to try putting it back outside. I mixed the water to change the temperature slowly, and put it back outdoors with the others. It immediately started moving around and eating again. I put the remaining fish outside with the same results.

Maybe they don't like the colour of the tub they were in? It was light grey, and their outdoor pond is black. Maybe they like natural light? Maybe they like the security of being with the big fish?