Do clownfish always live in pairs?

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Clownfish are always seen in pairs living in anemones on nature documentaries, but do they always live this way, and do I need a pair in my aquarium?

Not always. Studies on Amphiprion clownfish have suggested they occur in groups of a monogamous pair which live within a host anemone alongside several non-breeding subordinate clowns.

Clownfish are hermaphrodites. There are many types of hermaphroditism seen in marine fish, but clownfish are typically protandrous hermaphrodites. Initially they start off as males and one fish in the pair will become female. However, there’s more to it than that.

Clownfish live in groups consisting of a dominant female — the largest fish — and a smaller male with whom she pairs for life. The rest of the group comprises subordinate, non-breeding males.

If the female dies, or is removed, males grow quicker and one will change sex to become the new dominant female. She will then pair off with the largest sexually mature male to form a new monogamous pair.

In the aquarium, clownfish can successfully be kept as pairs, although some squabbling can occur, and in a large tank it’s possible to maintain them effectively as a group.

This item was first published in the September 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.