Check adult requirements
Record the baseline and check species, group size and adult size. Do not infer the aquarium's condition from a single sign. Confirm scientific identity, adult size, diet, social behaviour and swimming zone.
Then compare safe substrate, shelter and oxygenated current 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 nocturnal activity and compatibility with snails or slow 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.
Do not buy a loach for snail removal unless its group and adult needs can be met.