goldfish - Aquarium Hunter

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.

Fish Bowl Care: Safer Water and a Better Home for Your Fish

Trevor Aquarium Basics, Beginners (guides), Fish Care Guides, Water Health (info & tips) December 7, 2021September 24, 2026beginners, fish bowl, goldfish

A small, unfiltered fish bowl is not a suitable permanent home for pet fish. If you already have a fish in one, focus on water quality now and arrange an aquarium that meets the needs of its species. You do not need to find a tougher fish or add a cleanup crew.

This guide explains how to reduce immediate risks, clean without making conditions worse, and plan the move. It is a research-based care guide, not a claim that we have tested bowl keeping.

Why a small fish bowl is difficult to maintain

Small bowls leave little room for swimming, filtration and temperature control. Their limited water volume makes mistakes harder to manage. RSPCA Victoria advises keeping fish in properly equipped aquariums rather than small bowls, highlighting oxygen exchange and water-quality problems.

A larger vessel with suitable equipment still needs to meet the fish’s adult size, swimming and social needs. The word “bowl” on the packaging tells you very little about whether a setup is adequate. Choose the habitat for the fish, rather than choosing a fish to fit a decorative container.

If your fish is already in a bowl

Identify the species. Use its actual care requirements to choose the replacement aquarium. Start with our fish care guides.
Check the water. Measure ammonia, nitrite and temperature. Clear water does not establish that conditions are safe. Aim for no detectable ammonia or nitrite.
Address contamination promptly. Use partial water changes with properly conditioned, temperature-matched water if waste compounds are detectable. Retest afterward; a single change does not solve an ongoing waste problem.
Do not add more animals. Extra fish, snails or shrimp add to the demands on the setup.
Arrange a suitable aquarium promptly. Ask an experienced aquatic retailer or fish veterinarian for help if you cannot safely stabilize the current housing.

OATA’s freshwater setup guidance explains cycling, testing and maintenance. A newly purchased filter is not an established biological filter. Do not assume a new tank is ready simply because the water has stood overnight.

How to clean without adding new risks

Use an aquarium-only bucket and siphon to remove uneaten food and waste. Never use soap, detergent or household cleaning spray on occupied aquarium equipment. For routine cleaning, avoid repeatedly catching the fish and stripping everything down.

Treat replacement tap water for chlorine and chloramine according to the conditioner label, and match the temperature before adding it. If an established filter needs cleaning, gently rinse its media in removed aquarium water rather than disinfecting it. These precautions are covered in the RSPCA’s aquarium maintenance advice.

How often should you change bowl water?

There is no reliable once-a-week schedule for every bowl. The fish, feeding, volume and filtration all matter. Test at least daily while managing temporary unfiltered housing, and act on the results. Weekly maintenance advice for an established aquarium should not be treated as a guarantee for an unfiltered bowl.

Keep a short record of test results and water changes. If ammonia or nitrite keeps returning, seek help and improve the housing rather than repeatedly accepting unsafe readings.

Can a betta live in a bowl?

A betta’s ability to take air at the surface does not remove its need for clean water, space and stable warmth. The RSPCA recommends an aquarium of about 5.3 US gallons (20 liters) or more where possible, with appropriate filtration and heating. Its advised temperature range is about 75–79°F (24–26°C). A secure lid should leave access to air above the water.

For a beginner, an equipped aquarium of this size or larger is a better starting point than a tiny ornamental bowl. Read our female and male betta guide before planning companions.

What about goldfish, guppies or schooling fish?

This guide does not recommend any of them for a small bowl. Choose housing using the exact species’ adult requirements. A tiny juvenile’s current length is not a stocking plan, and a schooling species needs both appropriate companions and room for the group. Review the species before buying additional fish.

When a fish needs urgent help

Persistent gasping, loss of balance, unusual inactivity or rapidly moving gills deserve immediate attention. Check water quality and temperature, and ensure suitable aeration. Occasional surface breathing is normal for a betta; a sudden change in breathing or behavior is different.

The RSPCA fish-health guide recommends checking water first and contacting a specialist fish veterinarian for diagnosis and treatment. Do not assume every struggling fish needs medication.

Plan the replacement before buying extras

Prioritize a suitable aquarium, filter, test kit, conditioner and species-appropriate temperature control. Decorations come after those essentials. Our aquarium basics hub can help you plan the setup. If you cannot provide suitable housing, seek responsible rehoming advice from an aquatic retailer or rescue.

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

Disclosure: Aquarium Hunter may earn a commission from qualifying purchases made through links on this page, at no extra cost to you.

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.

Check price on Amazon

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.

Check price on Amazon

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.

Check price on Amazon

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.