The sight of a clownfish wriggling through the stinging tentacles of its anemone is a familiar and seemingly well-understood one to most people—the stinging anemone provides a protective home for the clownfish who is immune to such stings, and in turn the clownfish chases away any polyp-eating sunfish eyeing the anemone’s tentacles for a meal. But recent research has shown that all that clownfish wriggling significantly helps to oxygenate the anemone at night, when oxygen levels in the water are low.