How do you know if your convict fish is male or female?

When conditions are perfect for them they clean an area as a spawning place. The female lays, the male fertilises, and then they both take it in turns to fan the eggs and guard the perimiter of their area.. Once the fry are large enough the parents will select new spots to keep them in and will guard them until the fry are big enough to go off and fend for themselves.