Ask the moss on the indoor bonsai rockery to turn black?

Bryophyte is an aquatic bryophyte, green, and grows in wet places in water or land. Moss growing in rivers is called "Gai" in Dai language; Moss growing in still water ponds turns black due to natural reasons of temperature in high temperature season, and changes its shape instead of dying. Or the water body is rich and polluted seriously. The above is my personal opinion, I hope it will help you.