Goldfish (care) - Aquarium Hunter

Why Is My Fish Swimming Sideways? Causes and First Aid

Trevor Diseases (info & tips), Goldfish (care) September 20, 2023September 8, 2026goldfish disease, swim bladder, swimming sideways

Knowing why is my fish swimming sideways

A fish swimming sideways, upside down, spinning, or unable to hold its position is showing an urgent clinical sign—not a diagnosis. Buoyancy problems can follow poor water quality, low oxygen, temperature shock, injury, digestive or reproductive pressure, infection, organ disease, nervous-system disease, or a swim-bladder abnormality. Test the water immediately and contact an aquatic veterinarian when the sign is severe, persistent, or accompanied by breathing difficulty, swelling, wounds, pineconing scales, or appetite loss.

What to Do First

Observe before treating. Note whether one fish or several are affected, when it began, recent additions or maintenance, breathing rate, appetite, feces, swelling, wounds, and whether the fish floats or sinks.
Test water now. Check ammonia, nitrite, nitrate, pH, temperature, and—if available—dissolved oxygen and alkalinity. Ammonia and nitrite should be undetectable in a mature aquarium.
Increase gas exchange safely. Confirm the filter is running, remove surface obstruction, and add aeration if fish are gasping. Do not create a current so strong that the sick fish is exhausted.
Correct water problems gradually. Use temperature-matched, conditioned water. Avoid a sudden large pH change, especially in a neglected tank with suspected old-tank syndrome.
Isolate when appropriate. A cycled hospital tank can protect an injured fish and reduce disease spread, but moving a severely unstable fish can add stress.

Do not add antibiotics, salt, peas, laxatives, or temperature changes simply because a fish is tilted. The correct response depends on the species and underlying cause.

What the Swim Bladder Does

In many bony fish, the swim bladder is a gas-filled organ that helps regulate buoyancy. Some species can add or release gas through a connection to the digestive tract, while others regulate gas through the blood. Body shape and selective breeding can make certain goldfish more vulnerable to buoyancy problems. Some fish species have a reduced swim bladder or none at all.

“Swim bladder disease” is therefore an imprecise label. A fish may have an abnormal bladder, or another problem may be compressing, displacing, inflaming, or preventing normal control of it.

Common Causes of Sideways Swimming

1. Poor water quality or low oxygen

Ammonia toxicity, nitrite toxicity, extreme pH, temperature problems, excess carbon dioxide, or low dissolved oxygen can cause lethargy and abnormal swimming. Several fish becoming affected at once strongly suggests an environmental emergency. Test first rather than guessing from appearance.

2. Feeding and gastrointestinal pressure

Overfeeding, unsuitable food, or gastrointestinal distension may affect buoyancy in some fish, especially deep-bodied fancy goldfish. However, sideways swimming should not automatically be called constipation. Withhold additional treats while you test water and seek advice, but do not impose a prolonged fast or a week-long pea diet without species-specific professional guidance.

3. Injury

Collision with hard decor, netting, transport, aggression, or a jump can damage muscles, the spine, or internal organs. Look for bruising, missing scales, wounds, bent posture, or a sudden onset after handling. Remove obvious hazards and reduce stress, but do not manipulate the fish’s abdomen.

4. Infection or parasites

Bacterial, viral, fungal-like, or parasitic diseases can affect the nervous system, muscles, internal organs, or swim bladder. The same sign can have many causes, and laboratory testing may be necessary. Random antibiotics can fail, damage the biofilter, and make later diagnosis harder.

5. Organ enlargement, tumors, eggs, or fluid

Enlarged kidneys or liver, masses, retained eggs, internal fluid, and other abdominal changes can displace the swim bladder. Asymmetrical swelling, pineconing scales, protruding eyes, abnormal feces, or progressive weight loss make veterinary assessment especially important.

6. Nervous-system or developmental problems

Toxins, nutritional deficiencies, congenital deformity, and infectious neurologic disease can cause spinning, tremors, loss of balance, or abnormal posture. Newly purchased fish or multiple losses should prompt quarantine and professional diagnostic advice.

Supportive Care While Seeking Help

Keep temperature stable within the normal range for the species; never heat a cold-water fish to tropical temperatures as a generic cure.
Maintain clean, well-oxygenated water with gentle circulation.
Dim the light and reduce disturbance.
Lower the water level only if it safely helps the fish reach food or the surface and does not compromise the filter or heater.
Use a smooth, bare hospital tank when isolation is needed; protect the fish from abrasive decor and uncovered intakes.
If skin is continually exposed above water, seek veterinary advice quickly because drying and pressure injury can develop.

Why Common Home Remedies Can Be Risky

Peas

Peas are not a universal treatment for buoyancy disorders. They may add fiber for an herbivorous or omnivorous fish, but they are inappropriate as a cure-all and do not treat infection, injury, tumors, neurologic disease, or water toxicity. Carnivorous species have different dietary needs.

Aquarium salt

Salt does not broadly “prevent parasites and microorganisms.” Dose, duration, species tolerance, plants, invertebrates, and the actual diagnosis all matter. Never add an unmeasured “tiny amount.”

Antibiotics

Only use an antimicrobial when a qualified professional has identified a likely bacterial problem and selected an appropriate drug. Treating the display tank may harm beneficial bacteria and expose healthy animals unnecessarily.

Sudden warming

Raising a goldfish aquarium to 80°F (27°C) without a diagnosis can reduce dissolved oxygen and stress a cool-water species. Correct an unsafe temperature gradually, but otherwise maintain the species’ normal stable range.

When to Contact an Aquatic Veterinarian

Seek prompt help if the fish cannot feed or reach the surface, breathes rapidly, spins or convulses, is severely swollen, has pineconing scales, bleeding, ulcers, protruding tissue, a bent spine, or does not improve after water problems are corrected. Also seek help when several fish are affected or deaths occur.

Prepare the tank volume, species, stocking, water-test results, temperature, maintenance history, diet, new additions, medication history, and a clear video. This information is far more useful than the phrase “swim bladder disease.”

Prevention

Cycle the biofilter and test water regularly.
Perform routine partial water changes rather than only topping off evaporation.
Quarantine new fish when practical.
Feed an appropriate complete diet in controlled portions.
Keep intakes guarded and remove sharp or unstable decor.
Avoid sudden temperature and chemistry changes.
Observe every fish daily so subtle changes are noticed early.

Frequently Asked Questions

Is a fish swimming sideways always a swim-bladder problem?

No. Buoyancy and balance can be affected by environmental, digestive, traumatic, infectious, organ, or neurologic problems. Testing water and reviewing the whole clinical picture are essential.

Should I fast the fish for three days?

Not automatically. A short pause in feeding may be reasonable after obvious overeating, but prolonged fasting can harm weak or juvenile fish and will not treat many causes. Get species-specific advice.

Can a fish recover?

Some fish recover completely after an environmental or temporary feeding problem is corrected. Others need targeted treatment, and chronic structural or internal disease may not be reversible. Prognosis depends on diagnosis.

Final Advice

Treat sideways swimming as a warning sign. Test water immediately, stabilize oxygen and temperature, avoid guesswork medications and universal home remedies, and obtain aquatic veterinary help for severe or persistent cases. For related care, see our guides to ammonia poisoning, fish lying on the bottom, and safe water for goldfish.

Black Moor Goldfish Care: Tank, Diet and Health

Trevor Aquarium Basics, Fish Care Guides, Freshwater Fish (info and tips), Goldfish (care), Koi & Goldfish Care Guides, Ponds (info & tips) June 3, 2023September 16, 2026Black Moor Goldfish, goldfish

Black Moor goldfish are fancy goldfish with rounded bodies, paired tails and prominent telescope eyes. Their unusual eyes make them slower and more vulnerable than streamlined common or comet goldfish, so they need a spacious, fully cycled aquarium with gentle tank mates and smooth décor.

Care summary: Plan around the fish’s adult size rather than its size in the store. A practical starting point is at least 100 litres (about 26 US gallons) for one adult fancy goldfish, with roughly 50 litres more for each additional adult. Use efficient biological filtration, keep ammonia and nitrite at 0 ppm, and choose a long tank with open swimming space.

Black Moor goldfish at a glance

Scientific name	Carassius auratus
Type	Fancy telescope-eye goldfish
Expected adult size	Often 15–20 cm (6–8 in), depending on genetics and care
Temperature	15–23°C (59–73°F) is a useful routine range for fancy goldfish
Water quality	0 ppm ammonia, 0 ppm nitrite; keep nitrate controlled with maintenance
Diet	Quality goldfish staple plus suitable plant matter and occasional varied foods
Temperament	Peaceful, slow-moving and social
Typical lifespan	Many years; good care can support a decade or longer

What makes a Black Moor different?

Black Moors are selectively bred fancy goldfish, not a separate wild species. Their deep body, split tail and protruding eyes distinguish them from streamlined common goldfish. Young fish may be bronze or grey before developing darker pigment, and some adults become lighter or develop orange areas as they age. A colour change alone does not prove disease, but a rapid change accompanied by lethargy, appetite loss, abnormal breathing or damaged skin deserves investigation.

The telescope eyes are delicate and provide less effective vision than ordinary goldfish eyes. Black Moors may take longer to locate food, bump into sharp objects or lose meals to faster fish. Their care should therefore prioritise predictable feeding, gentle companions and an uncluttered layout.

Tank size and shape

Choose the largest practical rectangular aquarium. OATA recommends at least 100 litres for one adult fancy goldfish and an additional 50 litres for each extra adult. Treat this as a starting point, not permission to overcrowd: adult size, swimming room, filtration, oxygen, maintenance and test results all affect carrying capacity.

A long, wide tank offers more useful swimming space and gas exchange than a tall tank of the same volume. Bowls and small novelty tanks do not provide adequate room, filtration or environmental stability. Place the aquarium on a purpose-built level stand, away from direct sunlight, draughts and vibration. Remember that a filled aquarium is extremely heavy.

Filtration, cycling and oxygen

Goldfish produce substantial waste, so a filter is essential. Choose a unit with generous mechanical and biological media capacity, then adjust or spread the outlet if the current pushes the fish around. An air stone can improve circulation and surface agitation, but it does not replace filtration or water changes.

Complete a fishless nitrogen cycle before adding fish. Test the water regularly with a reliable kit. Ammonia and nitrite should remain at 0 ppm; rising nitrate signals that waste is accumulating and maintenance may need to increase. Rinse reusable filter media gently in removed aquarium water rather than untreated tap water, which can harm the bacteria the filter depends on.

Water conditions and maintenance

Fancy goldfish can acclimatise to a range of conditions, but stability matters more than chasing a perfect number. OATA lists 15–23°C (59–73°F) as an optimal range, with pH 6.5–8.5 and medium-hard water. Avoid abrupt temperature or chemistry changes.

Test ammonia, nitrite, nitrate and pH at least weekly, and more often in a new or troubled aquarium.
Change about 25% of the water weekly as a starting routine, adjusting according to test results and stocking.
Treat replacement tap water for chlorine or chloramine before it enters the tank.
Vacuum exposed areas of substrate to remove trapped waste.
Check filter flow, fish behaviour and temperature daily.

If ammonia or nitrite is detectable, treat it as a water-quality problem: stop adding fish, check the filter, reduce feeding temporarily if appropriate, and carry out condition-matched water changes. Persistent or severe problems need experienced aquatic or veterinary help.

Safe aquascaping for telescope eyes

Leave a broad central swimming area and inspect every object for sharp points, narrow gaps and abrasive edges. Smooth stones, rounded wood and robust live plants are safer choices. Avoid rigid plastic plants and rough ornaments that can scratch eyes or catch long fins.

Sand or smooth, appropriately sized gravel can work if it is kept clean. Do not use loose pieces small enough to be swallowed or large enough to trap decomposing food. Secure heavy décor so that digging cannot undermine it.

Feeding Black Moor goldfish

Use a quality food formulated for goldfish as the staple. Slow-sinking pellets or granules often make feeding easier for deep-bodied fancy goldfish and reduce frantic surface gulping. Offer a small portion the fish can finish promptly, watching to ensure the Black Moor actually finds its share.

Suitable variety can include daphnia, brine shrimp, bloodworms and modest amounts of soft vegetable matter. These additions should complement—not replace—a nutritionally complete staple. Remove leftovers because decomposing food degrades water quality. Persistent floating, sinking or abnormal posture is not automatically “constipation”; check water quality and consult an aquatic veterinarian when signs continue.

Compatible tank mates

The safest companions are similarly slow fancy goldfish of compatible size and temperament. Black Moors are often outcompeted by fast common, comet and shubunkin goldfish. Avoid fin-nipping tropical fish, aggressive species and very small animals that may be eaten.

Observe feeding closely after adding a companion. More fish also means more waste, so test water frequently and confirm that the aquarium and filter have enough capacity before expanding the group. Quarantine new fish in a separate cycled setup when practical, using separate nets and siphons.

Health warning signs

Check your fish every day. Warning signs include clamped fins, rapid breathing, repeated surface gasping, persistent bottom sitting, erratic swimming, appetite loss, white spots, ulcers, cotton-like growth, swollen tissue or an injured eye.

Test water first whenever behaviour changes because poor water quality is a frequent cause of illness. Do not add random medications “just in case”; different problems require different treatment, and some products can damage the filter or stress the fish. Isolate a bullied or injured fish when necessary and seek advice from an aquatic veterinarian for serious, persistent or unexplained signs. A ruptured, cloudy or markedly swollen eye warrants prompt professional assessment.

Breeding considerations

Sexing goldfish outside the breeding season is unreliable. Mature males may develop small breeding tubercles on the gill covers and leading pectoral-fin rays, while females can appear fuller when carrying eggs. Spawning involves vigorous chasing that can injure a slow or visually impaired fish.

Breeding should be attempted only with a separate, prepared setup and a plan for the resulting fry. Adults commonly eat eggs, and young fish require dedicated food, excellent water quality and substantial grow-out space.

Frequently asked questions

Can a Black Moor live alone?

Yes, one can be kept alone if the aquarium meets its environmental and behavioural needs. Compatible fancy-goldfish company can work well when the tank, filter and maintenance routine can support the additional waste.

Does a Black Moor need a heater?

Not usually in a stable indoor room within an appropriate range. A thermostatically controlled heater may be useful where the room becomes very cold or temperatures swing, but it should be paired with an independent thermometer.

Why is my Black Moor turning orange?

Genetic colour change can occur as the fish matures, and some Black Moors lose part of their dark pigment. Check lighting, diet and water quality, and seek help if the change is rapid or accompanied by skin damage or abnormal behaviour.

Can Black Moors live with common goldfish?

It is generally better not to mix them. Common goldfish are faster, grow larger and may outcompete a Black Moor at feeding time.

Final care checklist

Provide a long, spacious, fully cycled aquarium rather than a bowl.
Keep ammonia and nitrite at 0 ppm and maintain nitrate with regular water changes.
Use efficient filtration with a current the fish can comfortably manage.
Choose smooth décor and compatible slow-moving tank mates.
Feed a complete goldfish staple in controlled portions.
Investigate behaviour or eye changes promptly instead of medicating blindly.

Sources

Can Goldfish Live in Tap Water? Safe Water Guide

Trevor Goldfish (care), Water Health (info & tips) February 25, 2022September 4, 2026goldfish, goldfish water, tap water

Yes, goldfish can live in tap water—but only after it has been made safe for aquarium use. Municipal tap water commonly contains chlorine or chloramine. Both can damage a fish’s gills and skin and can also harm the beneficial bacteria in the aquarium filter.

For most homes, properly conditioned tap water is the simplest and most practical choice. Treat every new batch before it contacts the fish, match its temperature to the aquarium, and test its chemistry rather than assuming all tap water is the same.

Quick method: Fill a clean aquarium-only container, add a conditioner that treats both chlorine and chloramine according to the label and the full volume of new water, bring it close to the tank temperature, then add it during a partial water change.

Why untreated tap water is unsafe

Water utilities disinfect drinking water to control microorganisms. The concentrations used can be safe for people to drink but harmful to fish because water passes directly across their delicate gills. Chlorine and chloramine can also disrupt the bacterial colony that converts toxic ammonia into nitrite and then nitrate.

Chlorine and chloramine are not interchangeable. Free chlorine may dissipate under some conditions, but chloramine is more persistent and should not be expected to disappear simply because water is left standing. A conditioner labeled for both is the reliable everyday solution.

How to prepare tap water for goldfish

Check your local supply. Your water provider’s quality report may say whether chlorine or chloramine is used. Treatment practices can change, so choose a conditioner that handles both.
Use a clean container. Keep buckets and hoses for aquarium use only. Never use equipment that has held soap, detergent, pesticides, or household cleaners.
Measure the conditioner accurately. Follow the manufacturer’s label. Dose for the amount of tap water being treated unless the product specifically instructs otherwise.
Match the temperature. Bring replacement water close to the aquarium’s temperature before adding it. Avoid a sudden temperature swing.
Add water gradually. During routine care, replace only part of the aquarium water. Pour or pump it in without disturbing the fish or substrate excessively.
Test regularly. In the aquarium, ammonia and nitrite should both remain at 0 ppm. Monitor nitrate, pH, temperature, and, when relevant, hardness and alkalinity.

A suitable aquarium water conditioner works quickly when correctly dosed. More is not automatically better, so do not exceed the label unless the manufacturer explicitly provides an emergency dose for a specific use.

What if untreated tap water was added by mistake?

Act promptly, but stay calm:

Add an appropriate chlorine-and-chloramine conditioner according to its emergency or aquarium-volume directions.
Increase aeration and surface movement because gill irritation can make breathing difficult.
Test free and total chlorine if suitable tests are available, and test ammonia and nitrite because the biofilter may have been affected.
Watch for rapid breathing, gasping, lethargy, erratic swimming, excess mucus, cloudy eyes, or red and irritated gills.
Contact an aquatic veterinarian if breathing distress is severe or symptoms persist after the water has been made safe.

Do not respond by repeatedly adding untreated replacement water. If a water change is needed, condition the new water first. Avoid adding salt, antibiotics, or other medications unless a specific problem has been diagnosed; none of them neutralizes chlorine or chloramine.

Tap water chemistry still matters

Removing disinfectants is essential, but it is not the whole job. Tap water varies in pH, general hardness (GH), carbonate hardness or alkalinity (KH), nitrate, and dissolved minerals. Goldfish generally cope with a reasonable range better than many delicate species, but they do best when conditions are stable.

Test both the source water and the aquarium. If the pH, hardness, or nitrate level is unusual, investigate before making large changes. A sudden attempt to chase a “perfect” number can be more stressful than a stable, suitable value. If you need to adjust hardness, use a measured method and read our guide to softening aquarium water safely.

Do you need to age tap water?

No, not when you use an effective conditioner as directed. Historically, aquarists left water standing so free chlorine could dissipate. That approach is unreliable for chloramine, which is designed to remain in the water distribution system longer.

Aging water can still help it reach room temperature or release trapped gas, but it should not replace dechlorination. Boiling is also impractical and does not reliably solve chloramine treatment for aquarium volumes.

Is bottled water better for goldfish?

Usually not. Bottled-water chemistry varies by brand and source, and “purified” water may contain very few minerals while spring water may be quite hard. It is expensive for the large, frequent water changes goldfish require, and a label designed for human consumption does not guarantee ideal aquarium chemistry.

If bottled water is used temporarily, test its pH and mineral content and avoid sudden changes from the aquarium’s established chemistry. Properly conditioned tap water is generally more consistent and economical.

Can goldfish live in distilled or reverse-osmosis water?

Not safely as an unmodified long-term water source. Distillation and reverse osmosis remove most dissolved minerals and buffering capacity. Pure water can have unstable chemistry and does not provide the mineral profile expected in a freshwater aquarium.

Reverse-osmosis water can be useful when source water has a specific, confirmed problem, but it should be remineralized or blended under measured conditions. Do not use it merely because it sounds cleaner. Test GH, KH, and pH and make changes gradually.

Can well water be used?

Possibly, but it must be tested. Well water normally lacks municipal chlorine or chloramine, yet it can contain unsuitable levels of iron, copper, nitrate, salts, agricultural contaminants, or dissolved gases. Its pH and hardness may also differ greatly between locations and seasons.

Use a certified laboratory when contamination is possible. Aerate a sample before comparing its pH with the aquarium because dissolved carbon dioxide can make freshly drawn well water read differently. Never assume that water safe for human use is automatically suitable for fish.

What about rainwater?

Rainwater is not automatically clean aquarium water. It may collect air pollution, roofing residues, metals, bird droppings, pesticides, and other contaminants. It is also often low in minerals and buffering, which can make pH unstable. Unless its collection and chemistry are carefully controlled and tested, conditioned tap water is the safer choice for most goldfish keepers.

Goldfish need more than safe source water

Conditioning tap water does not cycle an aquarium or remove the waste goldfish produce. Goldfish are active, heavy-bodied fish with a substantial biological load. They need a spacious enclosure, a mature filter sized for that load, strong gas exchange, and regular partial water changes guided by test results.

Keep ammonia and nitrite at zero, control nitrate with maintenance, and preserve the filter’s bacterial media. Rinse mature media gently in removed aquarium water rather than chlorinated tap water, and never replace all of it at once. For equipment choices, see our guide to aquarium filter media.

A bowl or unfiltered container is not made safe simply by adding conditioner. Without adequate water volume and biological filtration, toxic waste can accumulate quickly.

Frequently asked questions

Can I put a goldfish straight into conditioned tap water?

Conditioning removes disinfectants, but a new aquarium must also complete the nitrogen cycle before fish are added whenever possible. Confirm 0 ppm ammonia and 0 ppm nitrite with a test kit. Match temperature and acclimate the fish carefully.

Should I condition the whole tank or only the new water?

Follow the product label. When water is treated in a separate container, the dose is generally based on that new-water volume. When untreated water is added directly while refilling, some products instruct dosing for the full aquarium volume. The manufacturer’s directions take priority.

Does a household drinking-water filter make tap water safe?

Not necessarily. Different cartridges remove different substances, and performance declines as media is exhausted. Unless the system is validated for the disinfectant in your supply and you can verify the output, use aquarium conditioner and test the water.

What water is best for goldfish?

For most keepers, the best option is stable, tested tap water treated for chlorine and chloramine. The aquarium should be fully cycled, filtered, well oxygenated, and maintained with regular partial water changes.

Key takeaway

Goldfish can thrive in tap water when it is properly conditioned and its chemistry is suitable. Neutralize both chlorine and chloramine, match temperature, test the source and aquarium, and protect the biological filter. Do not rely on standing water, bottled-water marketing, or visual clarity as proof that the water is safe.

This article provides general aquarium-care information. If a fish has severe breathing difficulty, loss of balance, extensive skin or gill damage, or persistent symptoms, consult a veterinarian experienced with aquatic animals.

Best Goldfish Food: 5 Current Staple Diets

Trevor Aquarium Basics, Aquarium Equipment, Food (info & tips), Food (reviews), Goldfish (care), Pond Equipment August 1, 2021September 3, 2026fish food, Goldfish Food 0 Comment

The best goldfish food is a complete diet that matches the fish’s size, feeding position and water temperature while producing minimal waste. Pellets, granules, flakes and gel foods can all work; consistent portions, variety and water quality matter more than promises of rapid growth or instant color.

Healthy goldfish ready for a measured feeding — Feed small, controlled portions and remove leftovers before they degrade water quality.

Quick recommendation: Fluval Bug Bites Goldfish Formula is the best convenient staple here. Repashy Super Gold is the most flexible option for fancy goldfish when you are comfortable preparing and storing gel food.

Quick comparison

Food	Best use	Format	Buying option
Fluval Bug Bites	Everyday staple	Slow-sinking granules	Check on Amazon
Repashy Super Gold	Fancy goldfish	Prepared gel	Check on Amazon
NorthFin Goldfish	Dense slow-sinking food	2 mm or 3 mm pellets	Check on Amazon
New Life Spectrum	Small sinking pellet	Pellets	Check on Amazon
TetraFin Goldfish	Small fish	Flakes	Check on Amazon

Choose a size the fish can swallow easily and check the current package for formula and feeding changes.

1. Fluval Bug Bites Goldfish Formula

Best for: a convenient complete daily food.

Bug Bites Goldfish Granules use black soldier fly larvae as a leading ingredient and sink slowly, which suits many fancy goldfish that feed below the surface. Fluval lists a 1.4–2.0 mm granule and a fiber-enriched formula. The pellet version is better for larger fish, while flakes suit small mouths.

Check Bug Bites on Amazon Manufacturer details

2. Repashy Super Gold

Best for: adjustable soft portions and variety.

Super Gold powder is mixed with boiling water to form a soft gel. Repashy directs users to mix one part powder with two to three parts water and store prepared gel for up to two weeks refrigerated or six months frozen. Cut it to the correct size, prepare it hygienically and remove uneaten pieces.

Check Repashy Super Gold on Amazon Preparation instructions

3. NorthFin Goldfish Formula

Best for: a compact slow-sinking pellet.

NorthFin offers 2 mm and 3 mm slow-sinking pellets and lists 36% minimum crude protein and 5% minimum crude fat. Choose the smaller size for young or small fancy goldfish and ensure every fish gets access.

Check NorthFin on Amazon Manufacturer analysis

4. New Life Spectrum Goldfish Formula

Best for: a small sinking everyday pellet.

Sinking food suits goldfish that readily forage in midwater or near the bottom. It can reduce frantic surface gulping, although buoyancy disorders have many causes and are not cured simply by changing pellet direction. Persistent floating, rolling, swelling or appetite changes require water testing and veterinary advice.

Check New Life Spectrum on Amazon

5. TetraFin Goldfish Flakes

Best for: small fish and easy portioning.

Flakes are easy to crush and spread across the surface but become soggy and disperse quickly. Feed a small pinch at a time, keep wet fingers out of the container and replace food that smells stale or has absorbed moisture.

Check TetraFin on Amazon

How much should goldfish eat?

Package instructions are a starting point, not permission to feed until fish stop begging. Offer a small measured amount, watch every fish and remove leftovers. Adjust for fish size, number, body condition, activity, water temperature and food density. Weighing a weekly ration is more repeatable than using pinches.

Outdoor pond fish require temperature-specific feeding decisions. Food may need to be reduced or stopped in cold conditions according to the diet manufacturer’s directions and fish behavior.

Variety, growth and color

A complete food should remain the base. Suitable extras can include blanched leafy greens, shelled cooked peas in modest portions and appropriately sourced frozen foods. Peas are not a universal medical treatment. Avoid bread, crackers, seasoned food and wild prey exposed to pesticides or parasites.

Healthy growth depends on genetics, space, water quality, temperature and balanced nutrition. Carotenoid ingredients can support natural coloration but cannot create pigment the fish does not genetically possess.

Feed without polluting the aquarium

Test ammonia, nitrite and nitrate routinely.
Use several feeding locations when one fish dominates.
Remove gel, vegetables and pellets before they decay.
Keep biological filter media wet and never replace it all during cleaning.
Store food sealed, cool and dry; buy a size that will be used while fresh.

Frequently asked questions

Are sinking pellets better than flakes?

Neither is universally better. Sinking food suits many goldfish, while flakes work well for small mouths. Size, freshness and quantity matter most.

Should pellets be soaked?

Follow the label. Brief wetting may soften food, but prolonged soaking can leach nutrients. Choose a smaller pellet instead of routinely soaking oversized food.

Why is my goldfish always hungry?

Goldfish are persistent foragers and commonly beg. Appetite alone is not a safe portion guide; use measured food and monitor body condition and water quality.

Final verdict

Fluval Bug Bites is the best convenient everyday choice here. Repashy provides the most control over texture and portion size, while NorthFin and New Life Spectrum are strong slow-sinking alternatives. TetraFin remains a practical flake when portions are kept tight.

Affiliate disclosure: Aquarium Hunter may earn a commission from qualifying Amazon purchases, at no additional cost to you. Recommendations are matched to the exact foods discussed.

What Fish Can Live With Goldfish? – 10 Best Goldfish Tank Mates List

Trevor Aquarium Basics, Aquatic Life (info & tips), Goldfish (care) July 19, 2021April 4, 2022goldfish, What Fish Can Live With Goldfish 0 Comment

What Fish Can Live With Goldfish?: Finding a suitable aquarium companion for a goldfish is possible, but you can’t just add a species!

There are some very important things to consider.

First, any fish added to the tank must thrive in the same environment as the goldfish, especially at water temperatures of 65ºF to 75ºF.

It is equally important that the fish get along with each other. What does that mean exactly?

A few things: The new fish will not harm the gold fish, the gold fish cannot eat the new fish, and the goldfish still has the space it needs to grow.

Each type of fish has different needs. For example, some fish like warm water, others like cold water, others like salty water, others do not. Since you want all of your fish to be healthy and happy, it is important to choose tankmates who like similar conditions.

What Fish Can Live With Goldfish?

10 Best Goldfish Tank Mates List

1. Other Goldfish

Adding another gold fish of the same size and type is one of the easiest ways to add another fish to your fish tank.

Keep in mind that goldfish are omnivores and can be predators. It is important that the tank mates are coordinated uniformly.

Be very careful with the size. Large goldfish eat smaller ones, so they must be the same size.

Also, fancy goldfish tend to move slower than common ones and are unlikely to compete for food.

2. Bristlenose Pleco

Bristlenose’s plecos are much smaller than common plecos, which can grow up to 15 inches. Therefore, the bristle plecos fall into a useful sweet spot that is small enough to fit in many goldfish aquariums without being so small that the goldfish can eat them.

Choosing a pleco that lives with your goldfish also has a great advantage: the plecos like to eat seaweed so that your tank stays nice and clean!

And while some plecos are known to suck on goldfish scales, which often leads to serious injury, this problem is rarely reported with Bristlenose Pleco.

3. White Cloud Mountain Minnows

The main reason White Cloud Mountain Minnows goes well with goldfish is that they are cold-water fish that perform well in the same environment as goldfish.

They pick fish and they don’t do well on their own, so you should add at least 3, although 6 is better.

White Cloud Mountain Minnows are also very fast and can generally flood gold fish, making them less likely to hunt.

4. Black Skirt Tetra

Advantages of keeping Black Rock Tetras with goldfish:

Black Skirt Tetras are robust and easy to care for.

They are fast and can reach goldfish if necessary.

Like the Platy, Black Skirt Tetras are usually too big for goldfish to try to eat.

Disadvantages of storing Black Rock Tetras with goldfish:

You need space in your goldfish tank for a school with six or more black rock tetras.

They are not always the most alive fish.

There is a certain risk that Black Skirt Tetra’s gold fish fins may get caught.

5. Rosy Barbs

Pink spikes like the same type of water as goldfish. They also become 4-6 inches long, so they also fit the size well.

They are not aggressive fish and leave their gold fish alone. They are too big for you to eat your gold fish.

Remember that pink spikes train fish and are very stressed when alone or in small groups. They must be kept in groups of at least 6.

6. Bloodfin Tetra

Advantages of storing Bloodfin Tetras with goldfish:

Bloodfin tetras are robust, very good for beginners.

They are also fast and can beat goldfish if need be.

Disadvantages of keeping Bloodfin Tetras with goldfish:

You need enough space in your fish tank for a school with at least 5 Bloodfin Tetras.

There is a certain risk that Bloodfin Tetras will suffocate goldfish.

At just over 5 cm, the Bloodfin Tetras are large enough to live safely with goldfish.

7. Rubbernose and Bristlenose Plecos

Both the rubber tip and bristle tip make excellent tankmates for a goldfish. Plecos are calm fish that generally leave your gold fish alone.

You spend most of the day eating rock and grass algae, which also helps keep your tank clean.

8. Checker Barb

Benefits of keeping tabs with gold fish:

The spikes are a calm fish that pairs well with community tanks.

They are fast, so elegant goldfish that tend to be slow swimmers can overflow.

Disadvantages of keeping concealer picks with goldfish:

Checkered spikes are big enough to live safely with goldfish. Therefore, there is a certain risk that larger goldfish will try to eat spikes.

You not only need space for one, but also for a Checker Barbs school.

9. Weather or Dojo Loaches

Weather loaches or dojo loaches are another great option as they are cold water fish that thrive in the same environment.

These loaches should be kept in groups of 3 or more and enjoy building. Therefore, make sure that they are covered with fine gravel or sand substrate.

The loaches also take up a lot of space by themselves, so you’ll need a fairly large tank to house them with goldfish.

10. Corydoras Catfish

Benefits of keeping Corydoras catfish with goldfish:

Corydoras chases food debris down the tank and eats it instead of letting it rot, which helps keep the tank clean

They are very peaceful and will certainly not cause any problems for your goldfish. The opposite does not necessarily have to be the case.

Disadvantages of keeping Corydoras catfish with goldfish:

Since your corydoras live at the bottom of the tank, you may have a hard time feeding them without your goldfish searching for food first.

Corydoras are school fish, so you need space to keep a small group.

As with other smaller fish on this list, there is a chance that goldfish will try to eat them.

How many fish can I add to a goldfish bowl?

So once you have a tank big enough for your goldfish, you’re probably ready to add your tankmates.

Overcrowding has many serious health effects. The more fish you have, the faster the water quality will decrease. Fish also become aggressive when overcrowded, causing injury and possible infection.

The amount of fish you can add to a goldfish tank depends on the type of fish. It’s best to spend time examining the fish you want to add to determine how much space they need.

It is a good idea to follow the rule of how much space your goldfish needs and then add additional gallons to accommodate the additional fish. Why?

Since the goldfish is quite a messy fish, overcrowding quickly leads to dirty water.

Carefully research the type of fish you want to add and make sure they have the space they need. If you choose a school fish, be sure to add enough to make it happy in your new home.

conclusion

Building a community tank around a gold fish is not easy, but with careful planning, you can. A carefully planned combination of fish in the right environment can lead to a successful aquarium that is fun to watch.

The most important thing is that you use a tank that is big enough for all your fish to thrive. Remember that goldfish need a lot of space for them. If you keep them in a tank that is too small, they will hamper their growth and shorten their life.

3 Best Goldfish Tanks: Spacious, Safer Choices

Trevor Aquarium Equipment, Fish Tank (reviews), Goldfish (care) April 3, 2021September 16, 2026goldfish, Goldfish Tanks 0 Comment

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Goldfish need substantially more swimming room, filtration and oxygen than bowls and small “goldfish kits” provide. The best tank is a wide, rectangular aquarium sized for the fish’s adult body length and waste load—not merely the number printed on a product box.

Short answer: For fancy goldfish, the Aqueon 40 Breeder offers the most useful footprint and freedom to choose oversized filtration. The Tetra 55-gallon kit provides more water volume and length for a pair of compatible fancy goldfish, although its filter may need supplementing. The Fluval Flex 32.5 is the most compact option here and is best considered for one fancy goldfish with conservative stocking and disciplined maintenance. Long-bodied common, comet and shubunkin goldfish usually outgrow these choices and are better planned for a much larger system or suitable pond.

Quick comparison

Tank	Best use	Important limitation
Aqueon 40 Breeder	Best overall footprint for fancy goldfish	Tank only; equipment and lid are separate
Tetra 55-Gallon Kit	More length and water volume	Narrower front-to-back; filter may need help
Fluval Flex 32.5	Compact all-in-one for one fancy goldfish	Smallest option; rear filter reduces swim space

Best goldfish tanks reviewed

1. Aqueon 40 Breeder — Best overall footprint

The Aqueon 40 Breeder is our best overall choice because its approximately 36-by-18-inch footprint provides more turning room and surface area than a tall tank of similar volume. That matters for bulky fancy goldfish and for oxygen exchange. Aqueon lists high-quality glass construction, clean silicone edges and black trim.

This is a bare tank, which is an advantage if you want to choose a filter with generous reusable mechanical and biological media. It also means you must budget for a properly fitted lid, light, stand, filter, thermometer, air supply if required, water conditioner and liquid test kit. Aqueon says a filled and decorated aquarium weighs roughly 10 pounds per gallon, so use a purpose-built, level stand and include drip loops on every electrical cord.

Pros: wide footprint; easy equipment customization; good surface area; standard shape makes accessories easier to source.
Cons: not a complete kit; only three feet long; unsuitable as a permanent home for adult common, comet or shubunkin goldfish.

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2. Tetra 55-Gallon Aquarium Kit — Best larger starter kit

Tetra’s current 55-gallon kit measures about 48 by 13 by 20 inches and includes two LED hoods, a Whisper PF60 filter, thermometer, 200-watt heater, net and starter samples. The four-foot length is useful for swimming, and the greater water volume gives more dilution and stability than the smaller tanks here.

The included heater is not automatically needed for goldfish; temperature requirements depend on variety, room conditions and stability. The supplied filter is a starting point, not permission to overstock. Goldfish produce substantial solid waste, so monitor ammonia, nitrite and nitrate and be prepared to add a second mature filter or replace the included unit with one offering more reusable media. Never replace all biological media at once.

Pros: four-foot swimming length; larger water volume; lids and basic equipment included.
Cons: only about 13 inches front-to-back; bundled filter may be limiting for a heavy goldfish bioload; heater may be unnecessary.

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3. Fluval Flex 32.5 — Best compact all-in-one

The Fluval Flex 32.5 is a compact all-in-one with app-controlled lighting, two independent three-stage media chambers and twin adjustable output nozzles. Fluval lists dimensions of about 32.5 by 15.35 by 15.75 inches and pump output of 214 gallons per hour.

Its filtration compartments provide useful media space, but they also reduce the display volume. This is the minimum and most restrictive option in our comparison, so we would reserve it for one fancy goldfish rather than treating the label volume as a stocking target. Angle the outlets to avoid forcing a slow-swimming fancy fish to fight a strong current, add prefilter protection if necessary, and test water frequently.

Pros: integrated multi-stage filtration; adjustable outlets; covered, tidy layout; programmable light.
Cons: least swimming space here; curved front and rear chamber complicate cleaning; unsuitable for long-bodied goldfish.

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How large should a goldfish tank be?

There is no responsible one-number rule for every goldfish. Adult body length, body shape, activity, number of fish, filtration, oxygen, maintenance and actual water quality all matter. The RSPCA advises at least 50 litres as a baseline and a tank at least four times the adult body length long and twice the body length wide, with more space for additional fish. Its UK guidance also notes that goldfish may need at least 60 litres each. Treat those figures as minimum starting points, not targets to crowd.

Fancy goldfish are shorter-bodied and slower than common, comet and shubunkin varieties, but they still need a large footprint. Long-bodied varieties can reach substantial sizes and are active swimmers; FishBase records a maximum length of 48 cm for Carassius auratus. Plan a much larger aquarium or suitable filtered pond from the start rather than relying on a temporary small tank.

Why footprint matters more than a tall shape

Goldfish swim horizontally and benefit from turning room. A wide rectangular tank also exposes more water surface for gas exchange. Bowls, jars and novelty tanks have little usable volume, limited filtration space and unstable temperature and water chemistry. They are not suitable goldfish homes.

Filtration and cycling

Goldfish excrete ammonia and produce abundant solid waste. Choose a filter with accessible mechanical media for debris and substantial biological media for nitrifying bacteria. Manufacturer tank ratings are broad marketing guides; the real test is whether the aquarium consistently maintains 0 ppm ammonia and 0 ppm nitrite with nitrate controlled by maintenance.

Cycle the aquarium without fish before stocking. A mature nitrogen cycle converts ammonia to nitrite and then nitrate. Use a liquid test kit and do not add fish simply because the filter has been running for a fixed number of days. Read our aquarium nitrogen cycle guide and goldfish filter comparison for more detail.

Stand, floor and electrical safety

Use a stand designed for the exact aquarium footprint and filled weight.
Place it on a level, stable floor; never allow a rimmed tank to overhang.
Keep outlets and power boards away from splash zones and form a drip loop in every cord.
Do not move an aquarium containing water, substrate or fish.
Check the tank and seams for damage before setup, then leak-test it in a safe area.

Setting up a goldfish tank

Rinse the empty tank with water only; never use household soap.
Install the stand, tank, filter, lid, thermometer and any air equipment.
Choose smooth substrate or a bare bottom that can be cleaned thoroughly. Avoid gravel small enough to enter a goldfish’s mouth but large enough to lodge.
Use smooth, stable decor and leave an open swimming lane.
Fill with temperature-matched, properly conditioned water.
Complete a test-confirmed fishless cycle before adding goldfish.
Introduce compatible fish conservatively and quarantine newcomers when possible.
Test water and perform regular partial water changes with substrate cleaning.

Frequently asked questions

Can goldfish live in a bowl?

No. Bowls do not provide adequate swimming room, stable water quality, filtration or oxygen exchange for long-term goldfish welfare.

Do goldfish need a heater?

Not always. Many goldfish do well at stable room temperatures, but some fancy varieties and cold rooms may require controlled heating. Avoid abrupt temperature changes and use a separate thermometer.

Can two goldfish live in a 20-gallon tank?

A 20-gallon tank is not a responsible permanent plan for two adult goldfish. It offers limited swimming space and little margin for their waste load. Choose a larger footprint based on adult size and verify capacity through water testing.

How often should the water be changed?

Use test results to set the schedule. Many goldfish systems need weekly partial changes and gravel cleaning, but stocking and filtration can require more. Any ammonia or nitrite reading calls for prompt corrective water changes and investigation.

Verdict

The Aqueon 40 Breeder is our strongest all-round starting point for fancy goldfish because of its useful width and customizable filtration. The Tetra 55 kit adds length and water volume for keepers who want a more complete package. The Fluval Flex 32.5 is a polished compact option for one fancy goldfish, but it provides the least margin and demands conservative stocking. For common, comet or shubunkin goldfish, plan substantially larger from the outset.