This week’s Fish of the Week is the common clownfish (Amphiprion ocellaris). Found in coral reefs off the coast of Australia and Southeast Asia, these fish form a symbiotic relationship with certain species of anemone in which they are found: the clownfish protects the anemone from being eaten by other species of fish, whilst the anemone provides the clownfish with protection from predators with its stinging tentacles. The clownfish remains unharmed by the anemone’s stinging cells (nematocysts) due to their specialised mucus coating, which the anemone recognizes as ‘friend’ and does not try to harm. All clownfish are born male and have the ability to turn female, although once they have turned they cannot change back. This often occurs when two males have paired off and the larger, more dominant male becomes female. Clownfish have been easily bred in captivity for many years which has led to many designer varieties, and has made them a relatively hardy marine fish. This, and their relatively small size, usually reaching around 11cm/4.3 inches, makes them great aquarium inhabitants.