A diver is placing "fish apartments" on the seabed on Sunday in Susoh, Indonesia. /VCG Photo

As one of the most important ecosystems on the planet, coral reefs are also the habitat and refuge of various species of fish. However, since the area of natural reefs has shrunk in the past few years, man-made "fish apartments" have been springing up across Indonesia. /VCG Photo

These apartments are used as new habitats, shelter and spawning grounds for fish that have been victims of the damaged coral reefs. /VCG Photo

These "fish apartments" are expected to be overgrown with coral in a few months' time, which experts say is faster than natural conditions. /VCG Photo