Fried mojarra is a whole flat fish, salted and rubbed with lime, then fried until the skin crisps and the flesh comes away from the bone. It is coastal Colombian home cooking at its simplest: four ingredients, twenty minutes, one fish per person. In the US, buy whole tilapia.
If you prefer a coating, dredge the fish in wheat flour or breadcrumbs after salting and before frying. Shake off the excess: a thick coating steams the skin instead of crisping it.