Clown Fish

What you're getting

Your clown fish live in groups within a single sea anemone, with a breeding pair at the top and younger males making up the rest of the household. Here's the thing: they're all born male, but when the group needs a female, the dominant male develops the reproductive organs to fill that role. If the breeding female dies, the next male in line steps up and becomes female, then breeds with one of the other males in the anemone. It's a bit of a reshuffle, but it works.