Hi. i have this greyish black film growing on my sand bed in my saltwater seahorse tank. If i leave it alone itgrows fine hairs. most days i turn it over into the sand. next day its back. you cant pick it up. It disintegrates if you touch it so thats why i turn it over. Ive read about black hair algae but that seems to be mostly in freshwater planted tanks. i havr no live plants. The only thing i will say is that lgaewhen saltwater ghost shrimp are not available for feeding i do buy freshwater ghost shrimp. but only put enough in for that freding otherwise i have theshrimp in a separate container. Could they be introducing the black hair algae into the tank?