Measuring the adult convict
A male convict cichlid grows to roughly five or six inches long, while a female usually finishes around four to four and a half inches, and both sexes build a deep, thickset body that makes them look more imposing than the measurement alone implies. The black vertical bars on a grey-blue body earn the fish its prison-uniform name, females add a wash of orange or gold across the belly once mature, and older males may develop a modest forehead hump. Shop juveniles at an inch or two give little hint of the finished animal, because a convict keeps filling out steadily on a good diet and reaches breeding condition well before it reaches full length, which is where most of the surprises with this species begin.
Size plus temperament is the real purchase
No honest answer about a convict's size stops at inches, because what arrives with those inches is one of the most determined personalities in the hobby. A single adult claims a cave or flowerpot as its headquarters and rearranges gravel, uproots soft plants, and sees off visitors with total conviction. A pair, which forms readily and breeds enthusiastically, defends a much larger area around its eggs and fry, and two six-inch-class parents can dominate a whole community tank, herding tankmates into the far end for weeks.
The tank those adult inches require
Plan around a fully grown male rather than the juvenile you carry home. A single convict or a breeding pair needs a tank in the region of forty gallons with a long footprint, solid rockwork or clay pots that create a defensible cave, and a lid that fits, since an excited adult can splash and occasionally leap during disputes. Filtration should be generous, because a thick-bodied five-inch cichlid eating heartily produces far more waste than slim fish of similar length, and regular water changes keep colours and appetite strong. Decor needs to be sturdy and either anchored or accepted as movable, because redecorating is a core convict behaviour, and plants that cannot be dug up or that float tend to survive better than carefully rooted arrangements.
Tankmates, or the case for a convict-only tank
Matching companions to an adult convict means matching attitude as much as size. Other sturdy Central American cichlids of similar dimensions can hold their own in a large, well-structured tank where every fish has an escape route and a territory, but small tetras, long-finned fish, and gentle species simply become targets or meals as the convict grows. Many keepers conclude, happily, that a pair alone in their own aquarium is the best version of this fish, because the courtship, digging, and devoted fry-herding that follow are some of the most engaging behaviour available in freshwater keeping. What a convict pair should never be is an unplanned addition, since a male and female bought as two pretty juveniles will very likely present you with hundreds of fry and a rearranged tank within the year.
Buying with the adult in mind
Choose convicts with bright eyes, full bodies, and clean fins, and decide before purchase which of the realistic homes you are offering: specimen fish, breeding pair with a plan for the fry, or member of a robust cichlid community with space to spare. That fry plan deserves a sentence of its own, because convicts breed so willingly that finding homes for generations of youngsters becomes the keeper's problem quickly. A well-housed adult, by contrast, is hardy, responsive to its owner, and full of character for years. If a proven pair ever changes keeper, KinsLe Transferrable Profiles move its spawning history, territory layout, and record of which tankmates it tolerated, so the next owner inherits a known quantity instead of a striped surprise.