Cosby / Opaline Three-Spot Gourami (Trichopodus trichopterus) – 3–7cm & XL

The Cosby Three-Spot Gourami is the marbled domestic form of Trichopodus trichopterus. In aquarium shops it is also called the Cosby Gourami, opaline gourami or marbled Three-Spot Gourami. Those names describe a colour form, not separate species. It is a substantial labyrinth fish with blue, silver, green and charcoal patterning, thread-like pelvic fins and an individual personality that can range from composed to territorial.

Quantity one buys one unsexed fish in the size selected above. It is not a guaranteed pair, breeding pair, male-and-female set or two-fish pack. Choose an available approximate size grade in the live selector. Colour, markings, fin shape and body proportions vary with age, sex, condition, lighting and the individual fish.

This is a hardy species when its adult size and temperament are planned properly, but it should not be treated as a small, automatically peaceful community gourami. Allow a tank at least 100 cm long, provide plant cover and calm access to the surface, and choose companions that can share the same water without competing for the same upper-water territory.

Cosby Gourami care at a glance

Care point	Practical guidance	Why it matters
Accepted identity	Trichopodus trichopterus	Trichogaster trichopterus is older scientific wording still common in the trade
Trade form	Cosby / opaline marbled colour form	Blue, gold, platinum and opaline fish can be forms of the same species
Adult size	Plan for up to 15 cm standard length	Juveniles sold at a few centimetres can become a much larger centrepiece fish
Aquarium	At least 100 cm long for one adult; roughly 160 litres gross or more is a useful starting footprint	Length, surface area and separate retreats matter more than a tall narrow volume
Temperature	22-28°C, kept stable	A stable point shared by all tank residents is safer than frequent adjustment
pH	6.0-8.0	The published range is broad, but sudden change is still stressful
Hardness	About 5-19 dGH	Match new fish gradually to stable, tested aquarium water
Flow and surface	Gentle to moderate circulation, calm upper areas and open air access	This labyrinth fish must be able to reach the surface easily
Diet	Quality prepared food with varied frozen or live invertebrate foods	Variety suits its omnivorous, micropredatory feeding biology
Social plan	One specimen is often simplest; groups need more space, cover and a defensible sex ratio	Males may contest other gouramis and breeding territories

These are planning ranges rather than instructions to chase a perfect midpoint. Test the aquarium you have, compare the needs of every resident, and make any necessary chemistry change gradually. A mature, stable tank is more useful than a newly adjusted tank that happens to show one ideal-looking number.

Cosby, opaline, blue and Three-Spot Gourami explained

The valid scientific anchor is Trichopodus trichopterus (Pallas, 1770), a member of the gourami family Osphronemidae. Older books, supplier lists and search results often use Trichogaster trichopterus. That older combination is useful for finding historical information, but it should not replace the accepted name on the listing.

The wild-type Three-Spot Gourami normally carries a dark mark around the middle of the body and another at the base of the tail; the eye is traditionally counted as the third spot. Selective breeding has produced several aquarium forms. The Cosby or opaline gourami has irregular marbled patterning that can obscure the neat spots. Blue, gold, platinum and lavender forms can also belong to this same species.

"Cosby" is therefore a trade-form name, not a collection locality or a separate taxon. The supplier reference identifies this stock as the opaline/Cosby form, but it does not supply a breeder, farm, generation, wild locality or genetic certificate. The page does not claim any of those details.

Sale unit, sex and size options

Each live size option is one fish. Selecting two as the basket quantity orders two unsexed fish; it does not create a confirmed pair. A behind-the-scenes pricing label and a gallery image containing two fish are not sale-unit evidence. Only the live variant selector, quantity control and this written statement define the order.

Size labels are approximate trade grades. They help compare current options but are not millimetre measurements of the exact fish picked for dispatch. An XL label is a relative stock grade unless the selector gives a centimetre range. A fish can sit near either edge of its grade, and normal body depth and finnage make visual estimates vary.

Can juveniles be sexed?

Mature males tend to develop a longer, more pointed dorsal fin, while females are often fuller-bodied with a shorter, rounder dorsal profile. These differences are less dependable in juveniles, unsettled fish and some domestic colour forms. This listing does not promise a particular sex.

How large will it become?

FishBase reports a maximum of 15 cm standard length and a common length of about 10 cm. Standard length is measured from the snout to the base of the tail, so total length can be greater. Plan around the larger published figure rather than assuming a shop-size juvenile will remain small.

Appearance and gallery-image boundaries

A settled Cosby Three-Spot Gourami usually shows an irregular dark marbled pattern over a blue, silver or greenish body. The exact balance changes with genetics, age, sex, mood, background, lighting and health. The long pelvic feelers are sensory fins used to investigate objects and other fish; they are not damaged whiskers.

The four protected gallery images are representative scenes. They illustrate the intended marbled form, but they are not photographs of the exact fish that will be dispatched. One scene contains two fish; this is a composition, not proof of a pair or a two-fish order. Another places the fish beside plants, but those plants are not a calibrated size reference. Use the variant selector for the size grade.

Natural history and the labyrinth organ

Trichopodus trichopterus is a Southeast Asian freshwater fish. FishBase reports it from the Mekong basin and broader Southeast Asia, with introduced populations elsewhere. It occurs in shallow, sluggish or standing waters, including wetlands, marshes, swamps, canals and seasonally flooded areas with abundant aquatic vegetation.

The species is an obligate air breather. Its labyrinth organ lets it use atmospheric oxygen as well as its gills, which is valuable in warm, slow water where dissolved oxygen can fluctuate. This adaptation does not make dirty or uncycled water safe. Ammonia, nitrite, excess organic waste and abrupt temperature change can still injure the fish.

Keep an open route to the surface and leave an air gap beneath a close-fitting lid. A cover also reduces escape risk and helps maintain a more stable, humid layer of air. Floating plants are useful shelter, but thin them so they do not form a sealed mat across the entire surface.

Aquarium size and layout

For one adult, start with an established aquarium at least 100 cm long. A common 100 x 40 x 40 cm tank holds about 160 litres before substrate and decor, which gives a useful sense of scale. More than one Three-Spot Gourami, a male with females or a busy mixed community should have appreciably more room; around 200 litres or more with a long footprint is the more forgiving direction.

Volume alone does not settle the question. The tank needs usable horizontal space, separate sight lines, surface access and enough biological filtration for every adult resident. A tall narrow aquarium can hold many litres while giving two territorial fish very little distance from one another.

Planting and hardscape

Use tall plants, floating cover, wood or smooth decor to divide the upper and middle levels into several visual zones. Keep open swimming and feeding routes between them. A bare tank makes a subordinate fish continually visible; a structured layout lets it leave an encounter without being trapped in a corner.

Filtration and current

Provide reliable biological filtration with gentle to moderate movement. A spray bar, baffled outlet or planted calm zone can prevent the entire surface becoming a fast current. Completely stagnant water is not the goal: circulation must still carry waste to the filter and support gas exchange.

Water parameters and maintenance

A defensible species range is 22-28°C, pH 6.0-8.0 and around 5-19 dGH. Choose a stable point that also suits the proposed companions. Do not move the aquarium repeatedly through the whole range or use unmeasured additives to force an exact number.

Before adding livestock, ammonia and nitrite should both be zero and nitrate should be controlled through testing, sensible feeding and regular partial water changes. Match replacement water closely for temperature, use a suitable dechlorinator, and preserve mature filter media rather than sterilising it during routine maintenance.

The aquarium water-chemistry guide explains the nitrogen cycle, pH, hardness and testing in more detail. New keepers should also complete the first tropical aquarium guide before choosing a stocking list.

Normal surface breathing or a warning sign?

A gourami calmly rising for air is normal. Repeated frantic gasping, clamped fins, loss of balance or several fish crowding the surface is not something to dismiss as labyrinth behaviour. Check temperature, ammonia, nitrite, circulation and filter operation immediately.

Temperament and social planning

The Cosby form is often sold as a community fish, but mature Trichopodus trichopterus can be assertive. Males may flare, chase or defend an upper-water area, especially around other gouramis or a bubble nest. Females and individual males can also vary, so there is no universal promise of peaceful behaviour.

Keeping one as the only large gourami is often the simplest plan. A carefully sexed group can work in a substantially larger, densely furnished tank, commonly with more females than males, but that advice depends on accurate sexing and enough escape space. Ordering several unsexed juveniles does not guarantee the required ratio.

Three-Spot Gouramis are not monogamous. A male may court a female and later drive her from the nest area. Never assume that two fish sold together will form a stable bond, and be ready to separate an individual if chasing becomes persistent or feeding access is lost.

Compatible tank mates

Choose robust, similarly sized community fish that use different parts of the tank and share the same water range. Avoid companions that are tiny enough to be intimidated, very slow at feeding, strongly fin-nipping, long-finned, or likely to contest the same surface territory. A compatibility label is only a starting point; adult size, group needs and the actual aquarium footprint still decide the result.

Companion type	Starting view	Checks before combining
Medium peaceful schooling fish	Often suitable	Use a full group, confirm adult size and avoid known fin nippers
Calm bottom fish	Often suitable	Match temperature and hardness, and leave enough floor space and food access
Another large gourami	High caution	Territory overlaps; sex, tank length, cover and individual behaviour matter
Betta or long-finned surface fish	Avoid as a default	Similar silhouette and upper-water territory can provoke conflict
Tiny fish or ornamental shrimp	Risky	This species eats small aquatic animals and may investigate or consume very small tank mates
Aggressive cichlids	Usually unsuitable	Fin damage, feeding pressure and incompatible territories are likely

Compare the broader Gouramis and Labyrinth Fish collection before deciding. The pale Silver Platinum Three-Spot Gourami and Gold Gourami are forms of the same larger species and therefore do not automatically solve a temperament or tank-size problem.

Feeding a Cosby opaline gourami

FishBase records zooplankton, crustaceans and insect larvae in the natural diet. In an aquarium, use a reputable flake, soft granule or appropriately sized floating or slow-sinking pellet as the prepared staple, then rotate suitable frozen or live foods such as daphnia, brine shrimp, cyclops or mosquito larvae from a controlled source.

Offer small portions once or twice daily, adjusted to fish size, temperature and the rest of the community. Food should be eaten promptly rather than collecting among plants. A varied diet is more useful than a large meal or a single favourite food. This fish is an omnivore with micropredatory habits, not an algae-control product.

Food type	Role	Watch for
Quality flake or granule	Regular prepared staple	Choose a size the fish swallows cleanly
Frozen daphnia, brine shrimp or similar	Dietary variety	Thaw a small portion and avoid adding excess packing liquid
Live food from a controlled source	Enrichment and conditioning	Wild-collected food can introduce contaminants or parasites
Plant-containing prepared food	Part of a varied omnivorous menu	Do not rely on this gourami to clear aquarium algae

Arrival, acclimation and the first week

Prepare the aquarium before dispatch day. Confirm stable temperature and water tests, dim the lighting, keep a secure lid ready and make sure the filter is running normally. Follow the acclimation instructions supplied with the order rather than extending the process while transport water cools or deteriorates.

After release, leave the fish quiet and keep the lights subdued. It may be pale, cautious or reluctant to feed at first. Offer a small familiar food only when it is swimming normally, then remove anything uneaten. Check that tank mates are not blocking the surface, food or planted retreats.

Health, quarantine and long-term observation

A healthy settled fish should hold itself level, move deliberately through the upper and middle water, surface without panic and show an interest in food. Clear eyes, intact scales and fins held normally are useful observations, but no single sign proves health on its own.

Use a separate quarantine aquarium for new arrivals when your household protocol allows it. A simple heated, filtered setup makes feeding, waste and symptoms easier to observe without exposing established fish. Do not medicate a display tank on the basis of a generic symptom list; test water first and seek an aquatic-experienced professional when the cause is uncertain.

Published hobby estimates for lifespan vary, commonly spanning several years. Genetics, early rearing, water quality, diet, social stress and disease history all affect the outcome, so the listing does not promise a fixed lifespan.

Bubble-nest breeding behaviour

This species is a surface bubble-nest spawner. A mature male may claim a calm area, build a floating nest and court a receptive female beneath it. FishBase reports that the male gathers eggs into the nest and guards them until the fry are free-swimming.

Nest care also increases territorial pressure. The male can drive the female away after spawning, which is dangerous if a small aquarium offers no escape. Breeding should use a separate, covered plan with gentle filtration, floating support, conditioned adults and a safe way to remove the female and later the male when required. It is not a casual outcome to encourage in a crowded community.

Cosby, Silver Platinum, Gold and Pearl Gourami compared

Fish	Identity	Appearance	Planning difference
Cosby / opaline gourami	Trichopodus trichopterus	Irregular blue, silver and dark marbling	Same adult size and territorial potential as other Three-Spot forms
Silver Platinum Three-Spot Gourami	Trichopodus trichopterus	Pale silver or platinum domestic form	Colour changes, but core species care does not
Gold Gourami	Trichopodus trichopterus	Yellow or gold domestic form	Not a smaller or automatically calmer species
Pearl Gourami	Trichopodus leerii	Pearl spotting and dark lateral line	Different species; generally selected for a calmer planted community, but still needs adult space

For a different species, compare the Pearl Gourami. The Red Paradise Fish is another air-breathing labyrinth fish, but it has its own temperature and temperament requirements rather than being an interchangeable substitute.

Ordering live fish from Tropical Fish Co

Choose the available size grade and basket quantity shown on this page. Quantity one is one unsexed fish. Live availability, price and dispatch choices are dynamic and should be read from the selector and checkout rather than from static care copy.

Eligible livestock orders are covered by the Live Arrival Guarantee when the policy conditions are followed. Read the current live-fish delivery and guarantee information before ordering so someone can receive and inspect the shipment promptly. First-time customers can use WELCOME10 for 10% off where the code is eligible.

The guarantee covers the arrival conditions stated in the policy; it is not a promise of a particular sex, pattern, future colour, social pairing or long-term outcome. Aquarium preparation and compatible stocking remain the keeper's responsibility.

Frequently asked questions

Is a Cosby Gourami the same as an opaline gourami?

Usually, yes. Cosby and opaline are trade names for the irregular marbled domestic form of the Three-Spot Gourami, Trichopodus trichopterus. Appearance varies between breeding lines and individuals.

Is Trichogaster trichopterus a different fish?

No. It is older scientific wording for the same species. Current taxonomic sources use Trichopodus trichopterus.

Does quantity one mean a pair?

No. Quantity one is one unsexed fish in the selected size grade. The two-fish image is representative artwork, not a sale-unit statement.

Can you guarantee a male or female?

No. Sex differences become clearer with maturity, and the current size-graded stock is sold unsexed unless a selector explicitly says otherwise.

How large does a Three-Spot Gourami grow?

FishBase reports up to 15 cm standard length. Plan the aquarium for that maximum even when buying a much smaller juvenile.

What is the minimum aquarium size?

Use an aquarium at least 100 cm long for one adult, with roughly 160 litres gross or more as a practical starting footprint. More fish, more gouramis or a busy community need more room.

What temperature should I use?

A stable 22-28°C range is supported for the species. Choose a point that also suits every companion rather than changing temperature frequently.

What pH and hardness are suitable?

Use pH 6.0-8.0 and around 5-19 dGH as the broad planning range. Stable, mature water and gradual acclimation matter more than chasing the midpoint.

Does it need a lid?

Yes, a close-fitting lid is strongly recommended. It reduces escape risk and helps maintain a stable layer of air above the surface while leaving the fish clear access to breathe.

Is an opaline gourami peaceful?

Not reliably. Many live in mixed aquariums, but mature males can be territorial and individuals vary. Tank length, planting, companion choice and observation are essential.

Can two males live together?

Two males can fight, especially in a short or open tank. Do not plan multiple males unless the aquarium is very large and structured and you can separate them if necessary.

Can it live alone?

Yes. One specimen as the only large gourami is often the simplest community plan and avoids relying on uncertain juvenile sexing.

Can it live with a betta?

Avoid this as the default. Both occupy upper water, and similar long-finned labyrinth-fish signals can lead to persistent conflict.

Will it eat shrimp?

Very small shrimp and shrimplets are at risk. The natural diet includes small crustaceans and other aquatic invertebrates, so this is not a shrimp-safe guarantee.

What should I feed it?

Use a quality prepared staple in an appropriate size and rotate small frozen or live invertebrate foods. Feed modestly and remove persistent leftovers.

Why does it gulp air?

The labyrinth organ allows atmospheric breathing, so calm trips to the surface are normal. Frantic gasping or several fish crowding the surface requires immediate water and equipment checks.

Are the photos of the exact fish?

No. The current gallery contains representative scenes. The dispatched fish can differ in markings, colour intensity, proportions and apparent size.

Sources used for this care profile

• FishBase: Trichopodus trichopterus species summary - taxonomy, distribution, habitat, size, water range, diet, air breathing and aquarium length.
• Eschmeyer's Catalog of Fishes: Trichopodus - valid combination and historical synonymy.
• Tropical Fish Hobbyist: Blue Gourami profile - domestic forms, setup, diet, adult size and behaviour.
• OATA: Gouramis and Paradise Fish care sheet - labyrinth-fish biology, aquarium preparation and general welfare.
• Fishkeeper: Blue Gourami - domestic forms, social behaviour, space, feeding and breeding cautions.
• FishBase reproduction summary - bubble-nest building and male parental behaviour.

Sources describe species-level biology and established aquarium practice. They do not certify the sex, breeder, locality, farm, exact pattern or future behaviour of an individual sale fish.