London Zoo is appealing to keepers of rare fish around the world to try to find a mate for an endangered tropical species.
The Mangarahara Cichlid vanished from the wild in Madagascar when the only river it lived in was dammed.
All three left in captivity are male.
If a female can be found, the zoo wants to start a conservation programme, but the quest is urgent because two of the males are old.
The last known surviving female of the species was killed by an aggressive male during a previous attempt to get the fish to breed.