Is your sea hare eating it? If it is this I believe it is Chlorodemsis. Fox face , scopas, tuxedo and variegated urchins don’t eat it. Hermits and turbo snails may but would count on it. Cropped short to the rock it may get grazed but not sure. Manual removal near impossible to get it all. Flucanazole didn’t dent it, grew faster from nutrients of other algae die off.
Peroxide 3% injected into the algae in tank with flow off, didn’t kill it. Lanthanum chloride injection didn’t kill it.
I had broken down the tank to start over. Had invasive encrusting sponge, aptasia and other crud on rock. Removed rock and set in bleach bath waiting to hit it with acid. I stumbled upon some dry rock for a good price and took the easy route. Guy said it was covered in algae so he bleached it. Rock looked pretty clean enough to use. In the meantime from stirring the sand bed, cleaning out the over flows, dosing lanthanum etc etc.. The tank ended up with Dino’s. So dosing nitrate , silica, no water changes, no skimmer, you get the idea. There was some bryopsis in there as well and figured Flucanazole would clean it up.
So in a bleach solution, the tuffs of the algae turn white and slimy on the top. While underneath stays green. Clean off the slime to expose the green. The same, turns white and slimes up covering itself. Four days in bleach, acid wash, back in bleach, still green. Peroxide 3% sprayed on then into peroxide wash and scrubbed. If this crap comes back after that I am gonna find a new hobby lol.
There was some rock I left in the tank as well as frags that had the crud growing in it. Removal from water and straight 3% peroxide on the spots took care of it. They’re still some growing on overflows and glass that needs manual removal as nothing is eating it. This week hope to get rock back in tank. Will run Flucanazole after reset for safe measures.
If it was me knowing what I know now and it’s not that bad, I would remove the rocks and treat them with peroxide
Hope this helps and someone can chime in with a better alternative.