Several different groups of gouramis can be found in most pet shops. These groups have different temperaments, ranging from the peaceful dwarf gouramis to the aggressive paradise gouramis. Despite sharing a family, these fish vary considerably.
Dwarf gouramis belong to the genus Colisa. These gouramis stay smaller than 2 to 3 inches and come in many beautiful colors, including several from selective breeding. These gouramis are very peaceful and get along well with members of their own species and other fishes. With dwarf gouramis, you only have to worry about other fish picking on them. These fish thrive in aquariums with other small, peaceful community fish.
Trichogaster gouramis grow larger than dwarf gouramis, ranging from 4 to 8 inches. This genus includes the pearl gourami, three-spot gourami and blue gourami. Male and female pairs get along with each other. These gouramis also usually get along with any other fish that won't bother them. However, male gouramis from this genus tend to fight among themselves. You also need to avoid any fin-nipping fish, which seem to find these long-finned fish irresistible.
Kissing gouramis reach 8 to 10 inches in length as adults. A group of six can comfortably share a large aquarium of at least 75 gallons. They generally get along among themselves and other fish. However, once a pair break off from the group to spawn, they typically get aggressive defending their brood and may need an aquarium of their own for the duration of their spawning.
Paradise gouramis, sometimes called paradise fish, include several species. These gouramis get very aggressive. You cannot keep more than one male paradise gourami per aquarium without them fighting. Generally, the males will attack other males and other species of fish, but may leave females of their own species alone. Females and juveniles can live in groups in aquariums and get along with other fish.
Gouramis from the Trichopsis genus go by several names. Some hobbyist call them "croaking gouramis" because of the noises they can make. Others call them "licorice gouramis" because of the black lines along the sides of some species in this genus. These gouramis are small, sometimes even smaller that dwarf gouramis. They have a very peaceful demeanor, to the point of being vulnerable to bullying. To keep these gouramis thriving, you should give them either a species-only aquarium, or extremely peaceful tank mates.
The giant gourami (Osphronemus gorami), sometimes just called the gourami, grows to more than a foot long. Despite this large size, it has a very peaceful demeanor. It gets along well with other large, peaceful fish. Keep in mind that it needs an aquarium at least six feet long to accommodate if you plan on keeping it with other large fish.