green algae?

there are small patchs of green algae on my rocks and the plastic of the overflow.
it looks like coraline algae but green and it wont come off if i try to clean it off

 

if it won't come off, it's more than likely coralline, comes in all different colors, green being one of them

 

I had some of this on my red sea also it was not corilene but like a lime green. I actually decided to put my fish in qt wichis is a 40 breeded biger so they dident mind. After 4 days of no food in the tank I could easily scrape it off. I also wondered the same thing as it looks like algea rather then corralline. It may be corralline but I think mine was from high phosphates and went away quickly. Mine could not be scrubbed off for the life of me!

 

oh ok
it looks ugly cause its on the overflow and not the glass.
i just wanted to know if they were bad for the tank

 

my coraline starts out green then red than pink and purple