ID of strange grey algae

[reefkeeper2]

I've had this algae growing in my tanks for years. The pics are bad, but it's fine branching, calcareous grey looking tough stuff. It will cover the rocks if I don't scrape it off and it doesn't come off easy. . The biggest problem is that it grows all around the base of corals and frags keeping them from attaching to the rock I've placed them on. The rockwork eventually looks grey and fuzz covered. Nothing seems to bother it and it grows in high and low light areas.
Any idea what it is? I can't find anything that looks quite like it anywhere.

 

[WheatToast]

Branching coralline algae; different species of coralline may feature geniculate (branching) or nongeniculate (plating or encrusting) growth forms. These are rare hitchhikers but are somewhat common from macroalgae vendors. Urchins might eat this algae.
https://www.live-plants.com/corallinefine.htm

 

[reefkeeper2]

Thanks. I thought it might be some kind of coraline. Haven't seen my urchins eat it though.