Four or more gouramis should be kept together. Gouramis thrive best when kept in groups, and four is the smallest appropriate group size. If you don’t have the space for four gouramis or more, try keeping them in pairs to prevent stress and boredom.
You should be careful not to overcrowd the tank. As a general rule, one inch of fish requires at least a gallon of water to live comfortably, so it all depends on what type of gourami you have. For example, you can keep five pygmy gouramis in a 15-gallon tank, but you’ll need a 55-gallon tank to keep five kissing gouramis.