What is this?

[Mariepbr]

I have what appears as a hard algae slowly taking over my rocks and I don't know what it is. My lights are just turning on so I used a spot light to highlight them... You get a better color idea. Amy info would be great.

 

[ca1ore]

Those kinds of growth are usually sponge. Indicative of a healthy tank even though it can be a pain.

 

[Mariepbr]

That hard green covering the rock is sponge origin? And would it take over? I've had my tank for over ten years.

 

[reef lover]

I agree sponge. That type os you see can cover most anything. Might want to do some manual removal to keep it at bay.