The short answer for a licorice gourami
Give a pair of licorice gouramis at least a 10-gallon tank, and step up to a 15- or 20-gallon for a small group. These are tiny, jewel-patterned gouramis from peat swamp forests, and on paper a smaller nano tank seems plenty for fish barely an inch long. In practice they are shy, slow, and territorial about hiding places, so usable sheltered space matters more than raw volume. A 10-gallon footprint fits several caves, a deep bed of leaf litter, and planted corners with room left for a courting pair to retreat from tankmates and from you.
Why blackwater conditions shape the enclosure
Wild licorice gouramis live in tea-stained, very soft, acidic water that barely moves, among submerged leaves and roots at the swamp edge. Males claim a small cave or hollow, display their red, black, and iridescent blue patterning at its entrance, and guard eggs laid inside. That behaviour explains the tank: still water from a gentle sponge filter, dim light filtered through floating plants, and multiple enclosed shelters so a group does not fight over the single best cave. In a bright, bare, fast-flowing small tank they stay pale, hug the substrate, and rarely show the colours that give them their name.
Soft water is the other non-negotiable. Hard, alkaline tap water in a perfectly sized tank still leaves these fish stressed and short-lived, so many keepers use remineralised soft water and let leaf litter and wood stain and buffer the tank gently.
Arranging caves, leaves, and calm in 10 to 20 gallons
Scatter small caves, coconut huts, and hollow wood pieces across the base, each screened by plants so a fish can slip in unseen. Cover the floor with dried leaves over sand, replace them as they soften, and add fine-leaved plants and floaters until the surface light is dappled. Feed small live and frozen foods near the shelters at first; newly settled licorice gouramis often ignore dry food and will starve quietly in a community tank while bolder fish eat everything. A species-focused tank, or one shared only with equally small and peaceful blackwater fish, gives them time to feed.
Keep the lid snug and the room-side traffic calm while they settle, and view them from a short distance in the first weeks. Colour is your progress report: as confidence grows, males darken, the blue spangling brightens, and fish begin patrolling cave mouths in the open.
Group size and signs the tank is failing them
A pair suits the 10-gallon; in the larger tank, a group with more females than males lets cave territories spread out. Persistent pallor, refusal of food after settling, or one male permanently exiled to a top corner signals shelter shortage or water that is too hard and bright, not a need for a bigger community. Patience fixes more licorice gourami problems than equipment does. For a fish this dependent on soft water values, leaf changes, and cave positions staying undisturbed, KinsLe Family Sharing puts those exact details in the shared profile so anyone covering care keeps the swamp calm intact.