Kissing Gouramis, also known as Kissing Fish (Helostoma temminckii), are medium-sized tropical freshwater fish comprising the monotypic labyrinth fish family Helostomatidae. These fish originate from Thailand to Indonesia.
Typical of gourami, the body is deep and strongly compressed laterally. The long-based dorsal (16 – 18 spinous rays, 13 – 16 soft) and anal fins (13 – 15 spinous rays, 17 – 19 soft) mirror each other in length and frame the body. The posterior-most soft rays of each of these fins are slightly elongated to create a trailing margin. The foremost rays of the jugular pelvic fins are also slightly elongated. The pectoral fins are large, rounded, and low-slung. The caudal fin is rounded to concave. The lateral line is divided in two, with the posterior portion starting below the end of the other; there are a total of 43 – 48 scales running the line’s length.
The most distinctive feature of Kissing Gourami is its mouth. Other than being terminal (forward-facing) rather than superior (upward-facing) as in other Gourami families, the Kissing Gourami’s mouth is highly protrusible as its family name suggests, the lips are lined with horny teeth. The gill rakers are also well-developed and numerous. The visible scales of the body are ctenoid, whereas the scales of the top of the head are cycloid. Kissing Gourami reaches a maximum of 30 cm in total length. There is no outward sexual dimorphism and is difficult to almost impossible to distinguish the sexes.
It is important to emphasize the particularity that this species has in its mouth: it has an additional joint between its jaw and the rest of the joints, known as the intramandibular joint. This type of joint is also present in other species of fish that feed on nutrients attached to the substrate. By increasing the angle of the opening of the jaw, this joint allows Kissing Gourami to access these nutrients.
Shallow, slow-moving, and thickly vegetated backwaters are Kissing Gourami’s natural habitat. They are midwater omnivores that primarily graze on benthic algae and aquatic plants, with insects taken from the surface. They are also filter feeders, using their many gill rakers to supplement their diet with plankton. The fish use their toothed lips to rasp algae from stones and other surfaces. This rasping action, which (to humans) looks superficially like kissing, is also used by males to challenge the dominancy of conspecifics.
Kissing Gouramis are also popular with aquarists for the fish’s peculiar «kissing» behaviour of other fish, plants, and other objects. Kissers of both sexes will often spar by meeting mouths and pushing each other through the water. Kissing Gouramis need a roomy tank to thrive; they grow rapidly, and juvenile fish will quickly outgrow smaller aquaria. Kissing Gouramis are territorial; some are tolerant towards fish of similar size, but others will bully, chase, and torment, causing significant stress on tank mates. Male kissers will occasionally challenge each other; however, the «kissing» itself is never fatal, but the constant bullying can stress the other fish to death. These fish may be useful as algae eaters to control algae growth. To prevent digging and to present enough surface area for algae growth, the substrate should consist of large-diameter gravel and stones. The aquarium’s back glass should not be cleaned during regular maintenance, as the Gouramis will feed on the algae grown there. Most plants will not survive the fish’s grazing, so inedible plants such as Java fern, Java moss, or plastic plants are recommended.