Blue Gourami

About the species

The blue gourami has a labyrinth organ, a special breathing structure above the gills that lets it take some of its oxygen directly from the air above the water. That means it can survive in water with less dissolved oxygen than most other aquarium fish tolerate, but it also needs regular access to the surface and warm, not cold, air above the tank.

What the labyrinth organ actually is

It's a modified tissue inside a breathing chamber above the gills that evolved in fish from the shallow, slow-moving, often poorly oxygenated waters of Southeast Asia. Even with good filtration and surface agitation, a blue gourami will regularly rise to the surface for a gulp of air — this is normal behaviour, not a sign of poor water quality.

Why the tank lid isn't a minor detail

Because the fish needs to breathe air right above the water regularly, a large temperature gap between the water and the air just above it can, over time, stress the delicate labyrinth organ tissue. The tank cover should therefore keep the air above the water reasonably warm and humid, not exposed to a draught or noticeably colder room air.

A stubborn streak once it matures

Blue gouramis tend toward territoriality that intensifies with sexual maturity, especially toward similarly shaped or coloured fish and toward other males of the same species. Some individuals can be noticeably more "spiteful" than others, so it's worth watching behaviour for a while after introducing new tankmates.

Space for an adult fish

An adult can reach up to roughly 15 centimetres, so the recommended minimum of around 80 litres applies to a single fish or a small group, provided there is dense edge planting and some floating plants for cover.

Diet — an easygoing omnivore

The blue gourami is a fairly generalist omnivore that in the wild eats zooplankton, small invertebrates, algae, and plant matter. In the aquarium it accepts almost anything offered — flakes, pellets, frozen, and live food — which puts it among the less demanding fish in terms of diet.

Water — one of the more adaptable gouramis

A sensible range is 24–30 °C, pH 5.5–8.5, with hardness spanning from soft to very hard water. That unusually wide range places the blue gourami among the hardiest and most adaptable aquarium fish, which is also the main reason it's so often recommended to beginners.

Tankmates

It pairs best with robust fish of similar size — barbs, larger characins, and other medium to larger gourami species. Small, slow, or long-finned fish are worth avoiding, since they can trigger territorial behaviour in a mature male.

Telling males from females

The easiest way to sex this fish is by the dorsal fin: males have a longer, pointed dorsal fin, while females have a shorter, more rounded one. Males also tend to be somewhat more territorial and more intensely coloured, especially around spawning time.

One species, many trade names

Blue, opaline, and gold gourami are not separate species but colour forms of the same species, Trichopodus trichopterus, produced through selective breeding. Basic care is identical across all of them; only the pattern and intensity of colour differ, which is useful to know before buying so a keeper doesn't expect different requirements from what look like different fish.

A nest made of bubbles

Like several other labyrinth fish, a male blue gourami builds a nest of air bubbles bound together with mucus at the water surface during spawning, where fertilised eggs are then kept. Successful nest-building needs a calm water surface without strong current, which is another reason this fish dislikes an overly forceful filter outflow.

Fry don't have a working organ yet

The labyrinth organ isn't fully developed in young fish during the first weeks of life, so fry rely almost entirely on their gills to breathe. That means a rearing tank for fry needs especially careful water quality and enough dissolved oxygen until the organ matures — only then does a young gourami start regularly surfacing for air the way an adult does.

Pros & cons