What is this tough dark brown algae?

[BradR]

It’s super tuff, dark brown, almost black. Wire brush doesn’t remove it. It grows on lighted areas but seems to prefer less lighted areas of the rock. Turbo snails help a little but not much with it. Tangs don’t eat it.

 

[tzabor10]

It’s super tuff, dark brown, almost black. Wire brush doesn’t remove it. It grows on lighted areas but seems to prefer less lighted areas of the rock. Turbo snails help a little but not much with it. Tangs don’t eat it.

Perhaps they are eating it down to the nubs. What you see is future snail and tang snacks

 

[BradR]

I guess the bottom line is more cuc is needed. There are a lot of 1/8” snails that only come out at night that somehow reproduced but focus mainly on the bottom. Gonna try more turbo snails