Check adult requirements
Record the baseline and check swimming length and adult size including the sword. Do not infer the aquarium's condition from a single sign. Confirm scientific identity, adult size, diet, social behaviour and swimming zone.
Then compare territorial males and sex ratio with livestock needs and recent changes. Look for genuine overlap in water, flow, territory and feeding throughout the year.
Assess compatibility and welfare
Adjust one variable and assess a secure lid, planting and compatible active fish before continuing. Keep a reference so the result can be compared. Plan the complete group and monitor feeding, breathing, injury, shelter and space use.
A short aquarium restricts swordtails even when nominal volume seems adequate.