Red Tail Giant Gourami (Osphronemus laticlavius)

Choose the red tail giant gourami only for a very large aquarium

The red tail giant gourami, Osphronemus laticlavius, is one of the true giants of the gourami family. Adults have a deep, almost oval body in dark blue-green to near-black, a snub-nosed head with a heavy jaw, and bright red edges and trailing filaments on the dorsal, anal and tail fins. FishBase and Seriously Fish both give a maximum of 50 cm standard length, so this is a fish only for keepers with the space and budget for a very large aquarium.

In return it becomes a calm, impressive centrepiece. Seriously Fish notes that giant gouramis can develop real personality and learn to recognise their owner. Like all gouramis it breathes air at the surface, and FishBase describes this species as an obligate air-breather. OATA adds that gouramis have a long ray on each pelvic fin that works like a whisker to feel their surroundings, which you will see as the two thread-like fins under the body.

Check the names and relatives

These four species make up Osphronemus, the only genus in its subfamily and by far the largest gouramis, as Wikipedia’s summary of the genus explains. Seriously Fish says the red tail is told apart from the common giant gourami by its red finnage and that the two need the same care. Compare it with our Gold Giant Gourami, browse the gouramis and labyrinth fish range and the labyrinth fish category, or see other big show fish among our centrepiece fish and rare and collector fish.

Know what you receive and what it becomes

One purchase supplies one live young red tail giant gourami in the size you choose: 7–8 cm or 9–10 cm. Sex is not chosen. The photographs show a grown adult to illustrate the species; a young fish looks noticeably different.

Compare the young fish with the adult

The adult description combines Seriously Fish and Wikipedia’s species summary, which also notes that females are duller than males. Seriously Fish describes the barred pattern of young common giant gouramis fading as they grow; the young of this species are less well documented, so expect some change. Young giant gouramis grow quickly, and OATA warns that very large fish need welfare planning before they are bought, including their whole long life. No lifespan has been published for the red tail, but Seriously Fish records the common giant gourami living for more than 20 years in captivity. Never release an aquarium fish into the wild.

Read our delivery and Live Arrival Guarantee information before ordering, and have the aquarium matured and running at temperature before the fish arrives.

Plan for a 50 cm adult from day one

Seriously Fish gives a base of 180 × 60 cm, with 60 cm of height, about 648 litres, as the absolute bare minimum for an adult, and says bigger is better. OATA’s gourami care sheet gives 400 litres or more for giant gouramis, and its care sheet for very large fish says such species often need more than 500 litres, or an indoor heated pond, and that an off-the-shelf aquarium is unlikely to suit them in the long term. We recommend the Seriously Fish figure as the minimum.

Run a four-step space check

1. Footprint: at least 180 cm long and 60 cm front to back, so a 50 cm fish can turn easily.
2. Volume: work out the true volume with our tank volume calculator; 180 × 60 × 60 cm is about 648 litres before décor.
3. Weight: each litre of water weighs about 1 kg, so 648 litres is roughly 648 kg before glass, rock and stand; check that the floor can carry it.
4. Everyone else: add all other fish at adult size in our stocking calculator.

Some keepers start a young fish in a smaller aquarium and upgrade later. If you do, have the final aquarium planned and budgeted from the start, because a fast-growing gourami kept cramped can turn aggressive; Seriously Fish links aggression in adults mainly to tanks that are too small.

Furnish for a large, powerful fish

Seriously Fish suggests water-worn rocks and large pieces of bogwood, with floating plants if you can keep them, although this fish may eat them and most other aquatic plants. OATA warns that very large fish can knock over décor, so rocks must be secured and heaters protected, and asks for gravel or sand without sharp edges that can be kept clean.

Secure every item

Because the fish must breathe air, OATA’s advice to leave at least a small gap between the water surface and the cover is essential, not optional. Keep the aquarium out of direct sunlight and away from draughts, heat sources and constant noise, and give it overhead lighting on a regular day and night.

Keep warm water stable

Seriously Fish gives 20–30°C with about 24–27°C as best, pH 6.5–8.0 and 5–25 dGH. OATA’s general range for gouramis is 20–28°C, pH 6.0–8.0, 4–12 dGH and 3–10 dKH. Aim for the overlap:

Separate habitat values from waste readings

For an aquarium of the minimum size in a room at about 20°C, Seriously Fish estimates 150–225 W of heating, spread over three heaters; splitting the heating also means one failed heater cannot overheat or chill the tank. Our article on tropical fish tank temperature covers thermometers and heater checks. Most treated UK tap water falls inside these ranges; test yours, compare it in our water matcher, and see the water chemistry guide for what each value means.

Filter for a very messy eater

Seriously Fish calls giant gouramis very messy and recommends two filters, each rated 1,295–1,620 litres per hour, turning the water over four to five times an hour. For a 648-litre aquarium that is about 2,590–3,240 litres per hour in total. OATA suggests several large filters or a pond filter for very large fish, to cope with the volume of solid waste. Mature the system fully before the fish goes in; our pages on the nitrogen cycle and understanding aquarium filtration explain the process.

Follow a weekly maintenance sequence

1. Test ammonia, nitrite, nitrate, pH and hardness, and check every heater’s reading.
2. Change at least 25% of the water, as OATA advises, siphoning waste from the substrate.
3. Dechlorinate the new water and match its temperature; with a tank this size, a hose and a mixing valve save heavy lifting.
4. Remove uneaten vegetables before they rot.
5. Clean filter media only in removed aquarium water, and never clean both filters on the same day, so the bacteria recover.

Feed a mainly plant-based diet

Seriously Fish describes the species as omnivorous and unfussy but primarily herbivorous by nature, accepting pellets, frozen foods and vegetable matter, and advises plenty of vegetables, a quality dried food and algae wafers. In the wild, adult giant gouramis eat mostly plant matter, including fruits, seeds, leaves and flowers from land plants as well as water plants and algae, with insects, worms, crustaceans and small fish taken too, according to Wikipedia’s summary of the genus. OATA advises food of a suitable size, fresh vegetables for herbivores, and feeding once a day only as much as is eaten within a few minutes.

Build one measured meal

• Young fish: Tropical Cichlid Herbivore Small Pellet and Tropical Green Algae Wafers.
• Growing and adult fish: larger sticks such as Tropical Cichlid & Arowana Medium Sticks, alternated with Tropical Spiru Tablet A.
• Vegetables: blanched courgette, peas, lettuce or spinach, removed after a few hours if uneaten.
• Frozen: Frozen Herbivore Fish Food as part of the weekly rotation.

Fast growth tempts keepers to overfeed. A steady, measured routine keeps the water cleaner and the fish in better shape than large, irregular meals.

Introduce it to a mature aquarium

Add the fish only when ammonia and nitrite read zero. OATA describes two methods for big fish. The floating-bag method: lights off, float the bag for about 10 minutes, then add small amounts of aquarium water over up to 20 minutes before releasing the fish. The bucket method: place the fish in a clean bucket or box and slowly siphon aquarium water in through an airline until the water matches, without letting it cool too much, then net the fish across. Our guide on how to acclimatise new fish covers both.

Use a first-week checkpoint plan

Choose tank mates too big to swallow

Seriously Fish describes the red tail as generally peaceful with other large fish but warns that it will eat smaller fish and that some adults become very aggressive, usually in a tank that is too small. It suggests knifefish, large barbs, catfish and loricariids, the suckermouth catfish family that includes plecos, as tank mates. OATA adds that very large fish should not be mixed with much smaller ones and that herbivores are more likely to be compatible than predators, though not always.

Screen each companion

Candidates from our range include the Clown Knifefish, the Tinfoil Barb, the Silver Shark (Bala Shark) and the Leopard Sailfin Pleco, all large fish in their own right that need the same kind of very big aquarium. Check every mix, at adult sizes, with our tank mates tool.

Watch for problems early

OATA describes a healthy fish as having clear, bright eyes, undamaged fins, intact scales, no ulcers or bumps, normal swimming and steady breathing. Warning signs include clamped fins, flicking against décor and shimmying. Note how often your gourami rises to breathe and how it feeds in its first weeks, so changes stand out later.

Pair each sign with an action

Understand breeding and the wild population

Seriously Fish says breeding has not yet been reported in aquaria and is presumed to follow the common giant gourami: the male builds a large nest of plant material, spawns nearby and carries the eggs to it, chasing the female away. In that species the eggs hatch in 24–36 hours, the fry swim freely three to five days later, and in the wild the male guards them for two to three weeks. A breeding attempt would need a very large aquarium or a tropical pond.

The species was first described in 1992 from fish in the aquarium trade: Eschmeyer’s Catalog of Fishes lists the holotype, held at the California Academy of Sciences, as aquarium stock from Bangkok. Its wild range is disputed. FishBase lists Malaysia and Indonesia, while the checklists summarised on Wikipedia restrict it to the Kinabatangan and Segama river basins in Sabah, Malaysian Borneo, and regard Indonesian records as errors. FishBase lists it as Endangered on the IUCN Red List (assessed 2019), and Wikipedia reports that an eight-year survey of the Segama caught only a few specimens. All the more reason to give every red tail giant gourami in an aquarium a home for life.

Answer Red Tail Giant Gourami buying questions

What is a red tail giant gourami?

It is Osphronemus laticlavius Roberts, 1992, one of four giant gourami species. Adults have a deep, dark body and bright red edges and filaments on the fins. It comes from Borneo and reaches about 50 cm.

How big does it grow?

FishBase and Seriously Fish both give 50 cm standard length, measured without the tail. The 7–10 cm fish you buy will grow far larger, so plan the aquarium for the adult.

What size aquarium does it need?

Seriously Fish gives a base of 180 × 60 cm, about 648 litres, as the absolute bare minimum for an adult, and says bigger is better. OATA’s general figure for giant gouramis is 400 litres or more; we recommend following the larger Seriously Fish figure.

Is it the same fish as the giant gourami?

No. The common giant gourami is Osphronemus goramy, a larger, widespread species. The red tail giant gourami is a separate species described in 1992, recognised by its red fin edges. Seriously Fish says their care is the same.

What does it eat?

It is omnivorous but mainly a plant eater by nature. Feed a quality herbivore pellet or stick, algae wafers and plenty of vegetables, with frozen foods as extras, once a day and only as much as is eaten in a few minutes.

Which fish can live with it?

Large, calm fish that are too big to swallow, such as knifefish, large barbs and big catfish including plecos, in a very large aquarium. It will eat smaller fish.

Does it breathe air?

Yes. FishBase describes it as an obligate air-breather, so it must always be able to reach the surface. Use a cover with a gap of air above the water.

How long does it live?

No lifespan has been published for this species. Seriously Fish says the closely related giant gourami can live for more than 20 years in captivity, so plan for a long-lived fish.

Which size will I receive?

One live young red tail giant gourami in the size you choose: 7–8 cm or 9–10 cm. Young fish are less vividly coloured than the adult in our photographs.

Consult the care references

• Seriously Fish: Osphronemus laticlavius — adult size, minimum aquarium, water values, filtration, heating, diet, tank mates and presumed breeding method.
• FishBase: Osphronemus laticlavius — accepted name, maximum length, air-breathing, range and IUCN Red List status.
• Eschmeyer's Catalog of Fishes: Osphronemus laticlavius — original description, holotype and the aquarium-trade origin of the type specimens.
• Wikipedia: Osphronemus laticlavius — summary of the published range in Sabah, appearance of adults and young, and conservation status.
• Wikipedia: Osphronemus — the four giant gourami species, their wild diet and their air-breathing organ.
• Seriously Fish: Osphronemus goramy — the closely related giant gourami: juvenile pattern, nest building and lifespan in captivity.
• OATA: How to look after gouramis and paradise fish — UK trade guidance on gourami water values, giant gourami aquarium size, air access and feeding.
• OATA: How to look after very large fish (tankbusters) — UK trade guidance for very large fish: aquarium volume, filtration, secure décor, covers and feeding.
• Tropical Fish Co delivery policy — current dispatch days and Live Arrival Guarantee terms.