This video says about itself:
The parrotfish is an interesting specimen. Not only do they change sex from female to male as they get older but parrotfish like blowing spit bubbles to sleep in.
A giant spit bubble sleeping bag.
In the morning the parrotfish goes about living its life on the reef, spending its day happily munching coral with its huge buck teeth. The fish grinds the coral down to extract the algae. Like all animals – what goes in must come out and the fish poops out the undigested rock as sand. A single fish can produce 200 lbs of sand a year.
From Wildlife Extra:
Corals need more parrotfish to survive
A decline in parrotfish and sea urchin numbers is a bigger cause of Caribbean coral loss than global warming, a new report suggests, and by increasing these populations the reefs have a chance of recovery.
These species are the area’s two main grazers and the loss of them breaks the delicate eco-balance of corals and allows algae, on which they feed, to smother the reefs.
“The rate at which the Caribbean corals have been declining is truly alarming,” says Carl Gustaf Lundin, Director of IUCN’s Global Marine and Polar Programme.
“But this study brings some very encouraging news: the fate of Caribbean corals is not beyond our control and there are some very concrete steps that we can take to help them recover.”
“We must immediately address the grazing problem for the reefs to stand any chance of surviving future climate shifts.”
The research was carried out by the Global Coral Reef Monitoring Network (GCRMN), the International Union for Conservation of Nature (IUCN) and the United Nations Environment Programme (UNEP).