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Goldfish Basics

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Dear valued members,

It has been our pleasure to be committed as members of the community, Aquariacentral.com to help other fellow members towards their questions pertaining goldfish care from compatibility to illnesses. To help us cope better with the number of similar threads appearing from time to time, although we do not mind answering the questions for you but which could help us cut our time from the repetitive questions, we would like to suggest that a few minutes be taken when reading the following articles and points taken which will help enhance better your understanding what the hobby is all about.

I. Aquarium Size, Variants of Goldfish and General Guidelines
A. Impracticality of “Traditional” Fishbowls and Aquarium Size Guidelines for Fancy and Pond Goldfish

B. Variants of Goldfish

C. Stunting Explained

D. Attitude/Behavior

E. Aquarium Location

II. Water Parameters, Nitrogen Cycle and Filtration
A. Nitrogen Cycle Explained

B. Importance of Filtration

III. Decorations
A. Live Plants

B. Fake Plants

C. Rocks

D. Substrate

IV. Tankmates

V. Foods

VI. Finale
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Aquarium Size, Variants of Goldfish and General Guidelines

Aquarium Size, Variants of Goldfish and General Guidelines
A. Impracticality of “Traditional” Fishbowls and Aquarium Size Guidelines for Fancy and Pond Goldfish

In China, for several centuries, it has been their tradition to place goldfish in their fishbowls. This trend continues until today and will continue so despite the attempted passing of the bill by several countries particularly in Europe to ban the use of fishbowls towards goldfish due to the number of incidence where goldfish die within a few days or even weeks as a result of ignorance shared by a lot of people who buy fish without doing their homework first. To understand better why the fishbowls became part of the Chinese tradition, in China, their ardor usually is not spacious thus large aquaria are not an option for them to keep their fish in. Round smooth bowls were designed with great effect including the fish in them that they become part of the ambiance. China is a temperate zone. Unlike the tropical areas, in temperate areas, goldfish do not eat a lot due to the low temperature wherein their metabolic rate decreases significantly and in turn, reducing the pollution.

Nowadays, a lot of hobbyists have access to larger house and lots and modern technology thus improving the life support systems further. They are able to accommodate large aquarium systems which benefit the goldfish greatly. Aquarium size is a very important factor that must be carefully planned as it greatly influences the potential of the fish to reach its adult size. Aside from that, this helps the fish utilize their excess carbohydrates that they accumulate from consuming foods containing excess carbohydrates. If you have heard the saying, “the solution to pollution is dilution”, the saying is indeed very true.

Goldfish are no stranger to severely deteriorating water conditions however like all other fish, they become prone to several health issues as a result of the poor water conditions. Unfortunately for the fish, they produce a heavy amount of urea and feces especially when their metabolic rate is increased due to the elevated temperature. As a result, the water quality deteriorates rather rapidly especially when the tank is rather less than ideal in size.

Considering goldfish themselves do not stay small (which is why fishbowls are impractical nowadays) at 8 to 24 inches range, a general guideline for fancy types should be at least fifteen gallons per fish whereas pond types need at least twenty gallons per fish. Previous debates have been offered that the fancy types need a minimum of at least ten gallons per fish. While this point of argument does prove itself feasible, giving more allowance for space would be a much better option for the goldfish.

The above paragraph does not mean you can freely utilize the spare fifteen and twenty gallon tanks for goldfish. Those tanks are still very limited and you cannot keep goldfish in isolation as these are sociable by nature and unlikely to thrive for a long time if deprived of their company. With the number of goldfish suggested at three as the possible minimum, a 55g would be a best starting point for fancy goldfish whereas 75g would be the minimum for at least two to three pond types.

B. Variants of Goldfish

As the goldfish has been bred for decades, many strains have been formed as a result of selective breeding. This in itself complicates matters further as the different body formation of the fish also requires a few perks in how you attempt to accommodate them to avoid any future issues that will prove detrimental to their health.

For instance, bubble eyes are famous for their large bulbous eye sacs that dangle below their eyes. The eye sacs are quite delicate and easily punctured hence you have to avoid sharp edged decorations if you want to keep their eye sacs intact. Although the eye sacs will normally heal themselves, the injured sac will usually look very different than the previous. A lot of round bodied types are prone to buoyancy problems due to the compressed organs brought about by their distended abdomen. There are many causes to buoyancy disorders which we can cover later on as we go further into this.

Fancy Types
Doubletail with dorsal fins
Black Moor/Demekin/Telescope/Globe Eye
Tikus Pearlscale
Crown Pearlscale

Doubletail without dorsal fins
Bubble Eyes

Pond Types
Singletail with streamlined body
Common Goldfish/Hibuna

Singletail with rounded body


C. Stunting Explained

Stunting is one of the most controversial subjects in the history of aquarium trade. Until now, it remains a debate with various theories given as to what causes the fish to stunt. This complication is brought by the fact that there are differnt variables that influence greatly the growth rate of the fish.

Stress is the number one factor that is quite overlooked when it comes to stunting issues being addressed. When a fish becomes stressed, it releases the hormones, norepinephrine and epinephrine in response to stress, both of which reduce the growth hormones greatly. Once the stressor has been removed, the fish may gain a growth spurt due to the rebound effect by releasing more growth hormones. For further scientific studies, the abstract can be found here. Another abstract describing further what stress is, can be found here.

Stress occurs because of various factors. One such factor to address is overcrowding. This is a very commonly done mistake in the aquarium hobby. Many people have the tendency to buy a lot of fish on impulse and forget that their fish are still on growing stage. In overcrowded tanks, fish cannot feel comfortable or secured because of constant activities which eventually stresses them and makes them more vulnerable to health issues. The lack of space prevents the fish from developing normally as they should have. Overcrowding also encourages the proliferation of parasites whether fatal or not thus the fish are extremely stressed by the constant infestations and secondary infections.

D. Attitude/Behavior

E. Aquarium Location

Location is another one of the factors to consider. Fish are extremely sensitive to sounds and movements. Sounds can travel by twice as much in water than in air and this can be quickly detected by the lateral line system found on the flanks of the fish which enables them to find their way around their surroundings.

Make sure your aquarium is located in a dark or moderately lit portion of area. Avoid placing the aquarium under direct sunlight. Why? Exposure to sunlight can cause the temperature to fluctuate a lot that the goldfish becomes agitated by the depleting oxygen, elevated temperature and rapidly deteriorating water conditions as a result of high metabolic rate. High temperature itself can lower oxygen levels and causes the fish to gasp to the surface as goldfish are heavy oxygen consumers.

Traffic area also affects the fish and can possibly stress them. Too many movements around the aquarium area can frighten and stress most fish as they become agitated by the constantly high traffic area although goldfish in general, can learn to interact with the presence of humans as these fish are highly intelligent animals.
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Water Parameters and Nitrogen Cycle

Water Parameters and Nitrogen Cycle

Water parameters must be given of utmost important so pay attention to this as this may seem complicated to those unfamiliar about it. Take note, whether the hobbyist knows a thing or two about it or not that for every aquarium setup, nitrogen cycle takes place. What exactly is nitrogen cycle?

A. Nitrogen Cycle Explained

To explain this, nitrogen cycle is a process wherein the wastes produced by the fish serve as ammonia source. Ammonia source is needed by the Nitrosomonas bacteria to be able to convert it into nitrite. Nitrosomonas bacteria that converts the ammonia into nitrite, the ammonia will simply elevate dangerously thus the fish suffers ammonia intoxication as indicated by listlessness, gill burns, “peppering” or development or black spots, clamped fins, gasping for air on the surface, red streaking on the fins and extreme flashing around due to burns suffered.

The next thing that will develop after Nitrosomonas bacteria, is Nitrobacter bacteria once nitrite source becomes available. This other strain of beneficial bacteria helps covert nitrite into nitrate, although nitrate itself is not the final byproduct of the nitrogen cycle yet.

Nitrite is another dangerous substance that can also cause the fish to become intoxicated. Usually, most references will cite the use of sodium chloride to battle the nitrite intoxication as chloride ions can inhibit the toxic effects of the nitrite however dechlorinated clean water will help equally as it reduces the nitrite thus preventing possible intoxication.

It has already been noted that nitrate is not the final byproduct yet. This is especially true as most of us tend to forget the nitrate will simply remain in the water elevating dangerously if not for the anaerobic bacteria (anaerobes) that help convert nitrate into the last byproduct, nitrogen cycle. So how do we culture the anaerobes? Simple. In freshwater setups, we do not whereas in saltwater setups, we do using deep sand beds. Why not? Anaerobes form best in dead areas of the substrate and filtration (especially during long power outage periods). Once the organic matter has accumulated and bound tightly where the anaerobes thrive, hydrogen sulfide also forms.

Hydrogen sulfide is an extremely powerful acid capable of performing pH steep dives which is extremely dangerous to the fish. As it also reeks of rotten egg odor, the acid can also pose a health hazard to the owner himself and thus is best avoided. A safer way to utilize the anaerobes is by using denitrators where the anaerobes colonize. The water containing high nitrate content is passed through the system where the anaerobes then convert the nitrate into nitrogen gas. The use of denitrator however is not necessary as water changes and use of plants will help reduce the nitrate which is why the use of plants and water changes is widely encouraged.

In the end, you want to make sure you have zero ammonia and nitrite with nitrate not exceeding 40 ppm if you are keeping fish in your tank. Ammonia and nitrite exceeding 0.25 are highly toxic especially if the pH is alkaline (more than 7) as the ammonia’s toxic effects were not deactivated by converting it into ammonium which only happens when the water becomes acidic (lower than 7). High nitrate level is a result of wastes building up and is extremely dangerous as it can push the fish’s immune system to a breaking point that they become susceptible to health issues and become easily stunted as well.

Just to clarify matters whether anaerobes are necessarily bad or not, anaerobes are part of the ecosystem and without them, life would not be balanced as they play a major role in body functioning, nitrogen cycle process, etc. They are responsible for the breaking down of foods in your stomach but they are also responsible for dental abscesses, flatulence and tonsillitis. Natural habitats especially freshwater bodies such as the Lake Malawi, anaerobes are present in deep sand beds where they help break down the nitrate into nitrogen gas as already mentioned earlier. Even if disturbances result in it releasing hydrogen sulfide, the chances of it affecting any fish within the vicinity adversely is rather minimal as it is greatly diluted in a large water volume than in an enclosed ecosystem such as the aquarium.

To be able to determine the exact ammonia, nitrite and nitrate levels, please be sure to invest yourself in a liquid test kit (Aquarium Pharmaceuticals in particular). From this point, biased views will be displayed towards the use of particular test kits. Why? Unfortunately, most test kits manufactured by some companies are none to reliable especially test strips and we are hoping as responsible hobbyists to point everyone new and/or returning to the hobby in the right direction and as much as possible, minimize the probable issues that may happen.

Although, in some cases, test strips have shown their reliability, in general, they tend to be rather misleading and do not give assurance to the owner that the water conditions are within expectations, therefore, these must be avoided altogether. If you can trust your stores to test the water sample for you, this is fine but be sure you understand what they are talking about. Purely comments such as “fine” are very vague. You need to make sure their test kit is a reliable brand, within expiration date and in good condition (albeit not contaminated or tampered with).

The last variables not explained well yet are the pH, KH (carbonate hardness) and GH (general hardness) although the pH has been mentioned a couple of times in conjunction with the toxicity level of ammonia as ammonia is readily influenced by the alkaline or acidic state of the water. Although goldfish have shown to be rather flexible to various water conditions due to generations of selective breeding in the trade for decades, they are found to do better in hard alkaline water than in a soft acidic environment.

B. Importance of Filtration

The filtration is extremely important. Goldfish garnered a reputation for being extremely dirty compared to the tropical groups but this is not always the case since they rival a lot of plecos and cichlids in terms of the amount of wastes produced. Since these fish are cold blooded animals, their body temperature is also similar to that of the water temperature. In cold temperature, their metabolism slows down thus they are unlikely to pollute the water any faster than in tropical conditions however this also slows down their growth in the process. Considering our current climate conditions, obviously the goldfish will have to cope with the high metabolic rate thus our water quality deteriorates rather quickly which is why filtration is pointed out as one of the aspects that should be prioritized.

Aim for a filtration turnover rate by as much as four times the actual water volume of your tank. You can never have too much filtration unless it begins to create a whirlpool effect or too powerful that the goldfish are swept around becoming stressed in the process, in which case, this must be avoided and necessary adjustments made to keep the environment friendly for the fish. Keeping goldfish is certainly not cheap and even if you do not agree, then goldfish may not be for you at all.

Filtration systems recommended include the use of canisters, gutters (overheads) and hang-on-back (HOB). HOB unfortunately is not sufficient. It is therefore recommended to include another type of filtration that is able to cope with the amount of wastes being vacuumed into the filter. Make sure your filter media is able to remove large grains of dirt to fine particles. It is highly suggested that filter floss or filter perlon be included to be able to remove the fine particles responsible for clouding the water. Be sure to check the output flow weekly and once you notice the output flow weakening, clean your filter immediately to avoid clogging the media.

In regards to cleaning the filter media, we have noticed some people use hot water or soapy water to clean their filter media. Neither of the two are totally advisable as the beneficial bacteria are destroyed in the process thus your tank becomes a hostile environment to your fish especially as the insufficient number of aerobic bacteria left is not able to cope with the elevating levels of ammonia and nitrite. What you should do is use your old tank water or dechlorinated tap water to clean out the filter media. It does not have to be thoroughly cleaned as most of the dirt in it is still beneficial for the setup. You need not replace the old filter media with new ones unless the old media is already worn out and beyond use.


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Live Plants

It has been almost every goldfish enthusiast’s dream to attempt mixing plants and goldfish together in the same tank without the latter trying to turn them into a salad bowl. Though this is a little tricky to achieve, it is not impossible to mix both contrary to popular belief that goldfish will eat almost any plant that you place in their tank. Please be sure to research every plant you like before attempting them. The use of live plants has been widely encouraged in the hobby as they help improve water quality, provide food and refuge for the fish and add up to the natural beauty of the tank setup.

The first thing to consider is the temperature. Most plants that thrive in the tropics are unable to tolerate the coldwater to subtropical (range of 58-76 degrees Fahrenheit) environment required by the goldfish. They tend to turn glassy and eventually wither away if the temperature becomes unfavorable for them.

Secondly, some plants need high lighting whereas others require moderate to low light conditions. With high lighting conditions, CO2 injection may be necessary to allow the plants to compete efficiently with the algae before algal blooms are expected which are a bane in almost every planted setup as they become unsightly in vast growths. Unfortunately, as goldfish are large oxygen consumers, the CO2 injection may not be useful here especially if your filter is creating powerful turbulence that disperses the CO2 out of the water column therefore rendering the CO2 injection useless.

Thirdly, goldfish are avid grazers. They tend to graze around the bottom in search for food. While floating plants and plants that attach to any decorations will not have an issue with this, rooted plants unfortunately are met by this problem and are likely uprooted in the process as the goldfish attempts to move the substrate aside as they dig around. If you hope to successfully establish the plants, plan ahead and start laying out the plants where they should be before you get your fish. This will give the plants a head start to firmly root themselves in their place. You could also place large rocks or weights near the roots but be sure there is aeration around that area to prevent choking the plant roots which will subsequently kill the plant.

It is wisely recommended for beginners to start with plants that are relatively easy to keep and are undemanding without the use of high lights and CO2 injection. Remember to take it slow and easy as it is important that a good and slow start will make your experience a fruitful one. For a good start, try to get floating plants such as Pistia stratiotes, hornworts, water hyacinths and duckweeds. Keep your tank open-topped as most of the plants mentioned do not like condensation droplets forming on their leaves particularly the Pistia stratiotes and will eventually rot quickly. Although the duckweeds are firm favorite salads by all goldfish, by the time they have reproduce enough to sustain their number, they will work excellently in consuming nitrate level thus improving the water quality like other species of floating plants suggested although nothing will still replace the water changes as the top method for reducing nitrate and other nutrients. The hornworts are unlikely to be consumed as they prickle the mouths of the fish as it does with other fish that are urged by the temptation to eat it. Duckweeds, water hyacinths and P. stratiotes reproduce rather quickly through runners and can quickly carpet the whole surface area so be sure to trim them out when necessary. Hornworts reproduce by cutting and with their brittle leaves and stems, they can be messy and can clog some filtration systems.

Java ferns, Java moss and anubias are also tough choices and with their rather unpleasant taste, they make wise choices for a planted goldfish setup. Although Java ferns and anubias are low light plants thus making them easier to keep than most species, they are extremely slow growers. They need to be tied with nylon thread, string or fishing line into place on a decoration but not too tightly that the rhizomes become severed. Java moss, on the other hand, do not need too much attention as it will readily attach on anything and carpet it completely so be sure to trim them down if you do not like a rather bushy plant area.

For rooted plants, a good suggestion would be an array of Cryptocoryne sp., Echinodorus sp., Vallisneria sp., Sagittaria sp., Egeria densa, Egeria canadiensis, Hygrophila sp., Nymphaea sp. and Aponogeton sp. As all are rooted plants, be sure that these are planted firmly to the substrate and the white crown is not covered entirely or the plants will suffer Cryptocoryne rot which involves the plant melting although it will eventually recover but this may take some time and is best avoided. Cryptocoryne species are far more prone to Cryptocoryne rot than anything else so avoid transplanting them around too much. Finalize the layout before you try to stick them where they should be. The first four plants mentioned reproduce by runners and can quickly carpet the setup in time depending on the conditions provided. Hygrophila sp. and Egeria sp. can be reproduced by cuttings similarly with hornworts although the latter is not purely a rooted plant and is best kept afloat. A lot of goldfish favor the Egeria densa so do not be surprised if you find this plant left with a stalk instead. The leaves are too much for the goldfish to resist. The last two plants suggested Nymphaea and Aponogeton reproduce by bulbs. The Nymphaea sp. especially is an extremely beautiful plant with lushy leaf growths and even sprout flowers on the surface if allowed so be sure not to enclose your tank with a lid if you want to see the flowers sprouting and adding up to the beauty of the goldfish setup. The bulb can be left on its own although burying it halfway down will help it establish firmly its ground. To allow the young leaves to grow well, the leafy stalks that reach the surface may need to be trimmed down and this also helps prevent clogging of the surface with too many floating plants.

Lastly, it must be noted that each person has a different experience in regards to a particular plant compared to another so what may work for one may not work for the other. This must be kept in mind at all times and consider this, goldfish are extremely personable and they tend to choose their food at their own will so it is not surprising a lone comet would chomp down water lettuce and hornworts while another avoids both plants entirely. As much as possible, be sure to test each plant and plan backups in case your attempt does not work. Some plants are quite rare and expensive so it may be advisable these ones are best avoided unless you have an unlimited source and do not mind losing a single plant or two with high market value.

Fake Plants

If you do not opt to try live plants, you could use silk plants. Make sure your choices of fake plants do not have sharp pokes, corrosive metal strips and anything else that may potentially injure or kill your fish. Some fake plants have been known to be responsible for the tattered fins. This must be avoided if you want your fish’s fins intact.


Next, we turn our attention towards the use of rocks and other decorations. Considering a lot of goldfish are rather prone to injuries especially sight-challenged variants such as celestials, bubble eyes and most strains with wen growths covering their eyes completely such as ranchus and lionheads, sharp-edged decorations are best avoided to avoid injuries that may become detrimental to the health of the fish.

Limestones, lava rocks and polyurethane decorations with sharp edges do not work quite well in goldfish setups at all as they tend to scrape the skin of the fish badly especially when the goldfish are in chasing rituals as they attempt to mate or play around. Small round rocks and small slates (with no sharp edges) will readily work. Some goldfish enthusiasts tend to stick to marbles, golfballs and round porcelain figurines as their fancy decorations for their setup. Whether you like it or not, it does work even though it clashes with the natural outlook that you may be looking for.

Pet stores sell a wide range of polyurethane decorations however bear in mind, while they are totally safe for aquarium use, some are still dangerous to particular fish that do not resist the temptation to get into trouble. For instance, most decorations have small nooks and crannies. While this does provide refuge for the smaller fish, some goldfish tend to slip into them and end up injuring or killing themselves as a result of their struggle in their attempt to get out of the decorations. Orandas, ranchus and lionheads in particular are prone to wen injuries especially when their heads are caught into the holes of the decorations causing their wens to become inflamed. Severe wen damage will probably require wen surgery depending on the severity of the injury and this should be avoided by removing suspected decorations. For information on wen surgery, it can be found here.

Some polyurethane decorations also have sharp edges which again, make them unsuitable for goldfish setups due to their potential of injuring the fish. Most decorations are notorious for building up dead pockets underneath them (especially when the tank has substrate in it). It is recommended that circulation of the air must be prioritized here to ensure the health and safety of your fish. Some decorations need to be drilled with small holes to allow the air to enter inside thus preventing dead pockets from forming. As much as possible, try to vacuum the areas where the decorations are located, every time, you perform a water change on your tank so the risk of danger is minimized.


Substrate is another thing that needs to be looked into. This has always been an ongoing debate regarding their potential to choke the fish especially as the fish shifts the pebbles around as they forage the bottom for food. Although fine sand is often recommended as it does not pose risk of choking as the goldfish forages the bottom, it can still be swallowed and may damage the internal organs if swallowed in large amount by accident by the fish. Fine gravel works equally well despite the risk of choking which fortunately is rare but that does not mean this probability can be overlooked due to the small statistics of such incidence. As far as thickness is concerned, unless you plan to make your tank planted, it is advisable to stick to an inch thick of substrate only or better yet, do not bother with substrate at all wherein barebottom setups are much easier to clean as the wastes can be siphoned without getting trapped between the pebbles. In the end, this is your personal choice. See which type of substrate fits best in your typical setup and schedule proper way of vacuuming the wastes without too much trouble.

1. Much easier to clean as the wastes are lighter than sand.
2. Makes it easier for most fish and invertebrates to burrow around.
3. Friendly to fish with delicate barbels.

1. If I change my mind on rescaping tanks, sand is a pain to remove.
2. Becomes compact easily and becomes potentially dangerous if it binds and forms anaerobic pockets. For this reason, you need to stir it r rely on your trumpet snails to do the job for you.
3. Can damage powerheads if the powerheads are turned on while the sand has not settled completely yet.

1. Allows oxygen to penetrate through plant roots much better.
2. Easier to remove if you change mind rescaping the tank.
3. Much easier to rinse around unlike sand before setting it up.

1. Pain to vacuum around as the wastes are trapped.
2. Most fish choke on gravel easily although this rarely happens.


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Next topic will cover tankmates that are compatible with goldfish. To make it easier to understand what makes each fish in general compatible or not, descriptions per group of fish will be added.

We would like to thank the following for making this section possible with their contributed experiences, opinions and suggestions.

Please do remember experiences will vary so what may have worked for most people, may not be similar to your own. Be sure to follow your instincts before attempting the combination.


Apple Snail

Apple snails are one of the few snail families that are truly compatible with goldfish particularly the large species such as Pomacea canaliculata and Pomacea diffusa. There are currently nine genera that exist although only about three have been found available in th aquarium trade.

For further information on basic care and requirements, you may click the following for particular species.
Asolene spixi
Marisa cornuarietis
Pomacea canaliculata
Pomacea diffusa
Pomacea haustrum
Pomacea insularum

Bristlenose Pleco (Ancistrus sp.)
Bristlenose plecos are just one of the few plecos that are truly compatible with goldfish with the possible exception of bubble eyes, celestials and most demekins whose eyes may be injured by the swimming activities of this pleco.

Unlike most plecos, bristlenose plecos consume mostly vegetable matter and some plants thus they will not likely focus their taste on slime coat as protein source which most plecos unfortunately do.

Due to their rather quiet demeanor, they are greatly recommended especially as they relish the algae and keep them under control. Most male bristlenose plecos are territorial but given the space and hiding places, such issue can be avoided. Female bristlenose plecos are much more docile than the males in general.

Creek Chubs (Semotilus sp.)
Works well with pond type goldfish and the less delicate fancy types. Best avoided with the more delicate types such as bubble eyes and celestials due to their rambunctious nature.

Dojo Loach (Misgurnus anguillicaudatus)
Dojo loaches are categorized as coldwater to temperate species thus making them an appropriate tankmate for goldfish. They do not require fast flowing waters unlike most other loaches.

For further information on their basic care and requirements, please be sure to check this link.

Fathead Minnow/Rosy Red (Pimephales sp.)
Works well with pond type goldfish and the less delicate fancy types. Best avoided with the more delicate types such as bubble eyes and celestials due to their rambunctious nature.

Golden Shiner (Notemigonus sp.)
Works well with pond type goldfish and the less delicate fancy types.

Nerite Snail
Nerite snails are another group that can be kept suitably with goldfish. Their thick shells and discreet personality of not exposing their soft tissues unlike the apple snails make them quite compatible for several fish that would otherwise not be compatible with snails. Unfortunately, they will not take to supplementary foods easily preferring algae and biofilm as their main course of diet so you may need to ensure that those types of foods are constantly available for them to eat.

On the other hand, nerites with spines on their shells are best avoided as these ones can injure the goldfish that may accidentally brush themselves on the snails' shells.

The following species are commonly available and are completely suitable with goldfish.
Neritina natalensis
Neritina turreta
Vitta usnea

River chubs (Nocomis sp.)
Works well with pond type goldfish and the less delicate fancy types. Best avoided with the more delicate types such as bubble eyes and celestials due to their rambunctious nature.

Trapdoor Snail (Viviparus sp.)
Trapdoor snails are classified as coldwater in general therefore making them quite suitable in goldfish setups. Unfortunately, these snails are finicky eaters preferring to consume only algae and decaying plant matter although a few can readily take vegetable matter.

Bettas need warmer temperature and will be unable to tolerate the constant activities by goldfish. Aside from that, a lot of goldfish grow quite big and may not hesitate to gobble their smaller tankmates. A few goldfish enthusiasts have managed to accomplish the combination however we advise beginners not try this for reasons stated above.

Chinese Algae Eater (Gyrinocheilus aymonieri)
Another fish often mistaken as suitable for goldfish especially when petstore employees often recommend them as algae cleaners. These are absolutely one of the worst possible tankmates for goldfish. It is true that the juvenile ones will industriously clean the tank of its algae but as they begin to mature, their taste for algae fades to be replaced by their hunger for protein source which is where the goldfish's slime coat comes into play.

Adult Chinese algae eaters are very belligerent and will harass the goldfish aside from sucking their slime coats making the latter more prone to skin diseases. Adult Chinese algae eaters garner a size length of 8-10 inches so small tanks will not suit them appropriately as well.

Clown Loach
Clown loaches are incompatible as they require a much warmer water at 80 degrees Fahrenheit and above. They are also finicky with their water conditions and prefer fast flowing conditions.

Common Pleco
This is yet one of the most frequently asked questions whether they are truly compatible or not. Unfortunately, this fish is truly subjective and while some may have successfully kept them with their own goldfish especially with pond types, it is best advised not to combine them with the fancy types which are much slower and easily victimized by possible slime coat sucking incidents.

Common plecos are also territorial by nature as they mature so unless there is plenty of space in your tank, common plecos are best avoided. They have already been reported to even destroy most goldfish by consuming them whether they were already weakened or not and a friend even reported his own common pleco ate one of his prized fancy goldfish.

Goldfish will not hesitate to swallow their smaller tankmates especially ones with spiny pectoral fins. Many incidents have been reported involving corydoras being swallowed by a goldfish. In cases like this, either will be lost. It is best that the prey must be cut off with a sharp scissors at the cost of its life to save the predator from choking to death. Chances are likely that the the predator may survive much better than the prey throughout this horrible ordeal.

Guppies are easily gobbled by larger goldfish although the adult ones may be able to escape their gobbling habits. Fortunately, some guppies particularly ones meant as feeders can tolerate the cooler temperature much better than the fancy ones that have been immensely groomed.

Hillstream Loach
Hillstream loaches thrive on fast flowing and clean waters, both of which may not easily be accomplished if goldfish are kept together with them in the same tank.

Koi are generally not a problem when kept with the pond types such as wakins, watonais, jikins, hibunas (common goldfish), comets ad shubunkins however they are not compatible for rather slow moving fancy goldies.

Kuhli Loach
Easily gobbled.

Malaysian Trumpet Snail
Easily gobbled and pose health hazards when swallowed by goldfish especially when they have a rather sharp conical shaped shell.

See corydoras.

Spiny Nerite Snails
Nerites with spines on their shells are best avoided as these ones can injure the goldfish that may accidentally brush themselves on the snails' shells. A few examples to name a few are Clithon corona, Clithon faba and Neritina juttingae.

Warmouth (Lepomis gulosus)
Warmouth are shy fish and probably will not appreciate the constant activity and inquisitive nature of goldfish.

Yoyo Loach
Reasons are similar to clown loaches. These are also very boisterous tankmates therefore they may not be tolerated by the much slower fancy goldfish especially if they start harassing the latter with their inquisitive nature.
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Food is one of the factors that are overlooked greatly by several enthusiasts. Never forget the saying, “you are what you eat”. Goldfish obviously need proper nutrition if they must be kept for a long time. I have noticed petstores in general sell cheap fishfoods which do not have the proper ingredients and nutritional value without influencing the body functions of the fish adversely. A lot of people buy them without bothering to ask whether that particular product is even suitable for tropical fish or coldwater fish. To them, as long as it fits their budget, it is okay but what if that particular brand becomes the culprit of digestive upsets and buoyancy problems suffered by the fish as a result of ignorance?

Floating Foods in Correlation to Buoyancy Issues
I had been questioning for some time what exactly causes buoyancy problems. This had been a mystery to me because I found myself hounded by this question every time someone asks me how his fish got buoyancy problems. Many people alleged floating foods are the main cause. I chose to believe this in spite of myself feeding my own fancy goldfish floating pellets. After conducting several researches, I found that some goldfish tend to become “floaty” when they are fed with pellets regardless of whether it is floating or sinking although some alleged their fish gets “floaty” with floating pellets and this was remedied only by using sinking pellets or gel foods.

In many cases, flake foods have been avoided by goldfish enthusiasts for two main reasons: a. floating, and b. vitamins cannot be retained in them. Both points are valid.

When flakes float, the fish tends to ingest air in the process thus when it becomes trapped in the GI tract, it can cause buoyancy issues to the fish in question. Flakes also contain air itself and can expand quickly. As quickly as the fish would eat, the flakes expand themselves inside the digestive system of the fish thus making the fish prone to bloat or constipation.

Unlike pellets, flakes cannot retain the vitamins that they have been injected with due to high surface area and exposure to air and light which destroy the vitamins in the process. Aside from that, vitamins are water soluble and can easily be leached out of the water. As vitamins are best obtained by ingestion, the fish may be unable to utilize all the needed vitamins if they leach out of the food.

Starchy Foods
Although this theory in the first paragraph for floating foods does have a valid point, I believe we should all look into the ingredients used. Considering some fish get unusually “floaty” with either floating or sinking pellets, it could be the ingredients that are easily the culprit yet overlooked.

So what makes the ingredients of the food the possible culprit? Several food analysts who studied the ingredients and guaranteed analysis of particular brands suggested that the starch-based foods are the culprit. A lot of food products contain starch. It is added in the food to weigh in the protein content needed by the young fish. While it does weigh in to the protein content, it contains very little nutritional value thus making it worthless for use despite the claims that it helps with fish growth due to the alleged high protein content. Even though goldfish do not have stomach and digestive enzymes needed to digest the food well, they have bacteria in their digestive system that help digest the foods and at the same time, producing gas as they digest the starch particularly soybean meal and yeast which when trapped, will cause the fish to lose its buoyancy partially or completely.

Unfortunately almost all food products contain starch or grain-based ingredients such as soybean meal, yeast, wheat flour, wheaten gluten meal, brewer’s dried yeast, soy protein concentrate, rolled oats, etc. The only way to choose your food products is make sure the wheat ingredients do not make up most of the top ingredients (preferably the first five) as the arrangement of the ingredients indicate chronological order of the ingredient portions taking up the food most to the least. If possible, stick to brands where fish meal and krill meal take up the top places followed by a few grain-based ingredients (although I would still minimize the amount of starch involved as much as possible).

Sugary Foods
Sugary foods are not necessarily bad. Most plant matter contains carbohydrates in the complex form. In fact, goldfish do convert carbohydrates into fat deposits and many of the heavier bodied varieties would not develop properly without the appropriate amount of complex carbs in their diets.

The problem comes with simple carbs. Simple carbs are smaller molecules, digest easily and therefore are easily converted to fats. Too much fats causes health problems in fish, reptiles, dogs, cats, just like in people. Heart disease, obesity, fatty deposits on the liver and other organs, hypertension, are all potential dangers of over ingesting simple
carbohydrates. So, while it is important for goldfish to have carbs in their diet, it is also important that they receive them from a plant matter source that is high in fiber to balance over all health.

Most vegetables, in their raw state, contain complex carbohydrates only. It is not until after they are cooked that the sugars convert.

Frozen Foods
As far as frozen foods are concerned, there is also a danger of a Vitamin B and thiamine deficiency, as freezing depletes those levels. That is why it is also important to use a multivitamin such as Centrum in prepared diets.
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Lastly (we hope you are not bored yet as you continue reading this topic), we would like to remind everyone that despite our efforts to maintain the tank clean and healthy for the fish, health issues are inevitable and will certainly happen from time to time and even without warning. In this case, we hope to be able to help by posting your problems in this forum. For further inquiries regarding your problems, we suggest that you read this diagnostics thread which will help you track down possible issues and freshwater disease guide where more than 40 health problems have been identified.

If you have any questions, please do not hesitate to ask. This is why we are here for. It is our mission as members here to help those who truly are in need of help.
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