Start From the Gourami's Size and Temperament
A blue gourami — the blue form of the three-spot gourami — grows to five or six inches and carries a personality to match, especially in males, who can be pushy with anything slow, small, or similar-shaped. Tank mate selection is therefore a matching exercise: companions should be big enough not to be food, fast or confident enough not to be targets, and peaceful enough not to provoke a fish that will answer back. In a roomy tank, that formula produces a calm community; in a small one, the same gourami dominates every level and no mate list can rescue the stocking.
Companions That Work at Each Level
At mid-water, choose medium tetras with deeper bodies, rainbowfish, swordtail-sized livebearers, or a sensible school of peaceful barbs, all in groups big enough to be confident. Below the gourami, corydoras in a proper shoal, smaller peaceful loaches, and a bristlenose-type pleco occupy the floor without challenging it. Near the surface, the gourami itself is the feature fish, and it is wisest left as the only labyrinth fish in the tank. Each layer minding its own space is the pattern to aim for, since most blue gourami trouble starts when another fish contests the surface territory it patrols.
Fish to Leave Off the List
Tiny fish are snacks in waiting: neon-sized tetras, baby livebearers, and small shrimp will be hunted by a full-grown blue gourami, however peaceful it seemed as a juvenile. Fin-nippers are the opposite problem — tiger barbs in small groups and nippy serpae-type tetras will worry the gourami's long, trailing pelvic fins until stress and infection follow. Other gouramis are the classic mistake: a second male, or a gold or opaline form of the same species, reads as a rival, and males will fight over surface space and bubble-nest sites. Long-finned, slow fish such as fancy guppies and bettas combine both problems at once.
Sex, Space, and Surface Territory
A female blue gourami is usually rounder, duller, and markedly more tolerant than a male, and a pair or a male with two females in a large, well-planted tank spreads his attention. Floating plants and tall stems let him build and guard a bubble nest in one corner instead of claiming the whole surface, and breaking the tank into planted zones gives subordinate fish genuine escape routes. If chasing becomes relentless — one fish always hiding, fins torn, food never reached — the honest fix is a divider or a second home, not another week of hoping it settles.
Feeding a Mixed Tank Fairly
Blue gouramis are enthusiastic surface feeders, so in a mixed tank the practical risk is the gourami eating everyone's share while bottom fish wait for what never falls. Feed the surface first in one corner, then drop sinking food at the opposite end for corydoras and loaches, and watch whole feeding sessions weekly to see who actually eats. Keep notes on which new fish settled and which combinations caused chasing, because that history is what the next stocking decision depends on. KinsLe Family Sharing keeps those tank notes and the gourami's care details where every family member can see them before adding anything new.