A bigger fish than the shelf label suggests
Pearl gouramis grow into substantial fish — four to five inches of deep, slow-moving body — and they carry themselves like it, patrolling a loose territory rather than darting around it. Thirty gallons is the minimum that gives one pearl, or a male with one or two females, room to cruise, turn and retreat from each other, and the tank should be longer than it is tall. Anything smaller crowds a fish that cannot fold itself away, and a cramped male turns his frustration on tankmates he would otherwise ignore, shredding the peaceable reputation the species is sold on. The juveniles in the shop, pale and barely two inches, give no hint of the presence they develop; buy the tank for the adult.
Air, surface and still water
Pearls are labyrinth fish: they rise to the surface to sip air, so open, calm surface water is a need, not a nicety, and floating plants that soften the light overhead suit them perfectly — wild pearls live in swampy, plant-choked, slow water. Keep the filter flow gentle, since current pushes against their long, trailing ventral fins and keeps them perpetually braced instead of drifting. Those thread-like fins are feelers in the truest sense; the fish uses them to taste and test whatever it approaches, reaching out to touch plants, objects and other fish. Frayed or shortened threads are an early visible sign that a tankmate is nipping at a slow fish that cannot retaliate, and they are worth checking whenever you are at the glass. Keep the waterline a little below the rim, too, so the layer of air the pearls gulp at the surface stays warm and humid under the cover glass — a labyrinth fish breathing cold, dry room air is working harder than it should.
Sexing and grouping without trouble
Males carry the stronger orange-red flush on the throat and chest and a longer, more pointed dorsal fin; females are rounder through the body and plainer in colour. One male with two females spreads his courtship attention and is the classic minimum-tank arrangement. Two males need far more space and heavy planting to divide the tank into separate claims, and even then one usually fades, eating less and hiding more. A settled male may build a bubble nest among the floating plants — entertaining to watch, strand by strand — but he will guard it, and in a minimum-size tank the females need dense planted retreats at the far end while he does, or the guarding becomes harassment with nowhere to go.
Records that travel with the fish
A pearl bought as a shy juvenile will be moved, rehomed or left with a sitter at some point across the years it lives with you, and its size, sex mix and surface setup are exactly the details that get lost between one keeper and the next. A receiving keeper who does not know the fish is a surface-breather with a tankmate history can undo a good setup in a week. Keeping the pearl's measurements, grouping and tank arrangement recorded in its KinsLe Pet Passport means anyone caring for the fish inherits the full picture rather than a stranger's guess.