what is it?

[Joe-salt]

branch like red stuff all over live rock

 

[crazybizzle]

not really sure either but i like the colour of it.

 

[Kleko]

I think its alge. I have a lot of purple alge in my tanks over the rocks it gives it a nice finish. Im sure thats what your have in your pictures but im new to this hobbie also, so ask a pro

 

[Cal_stir]

if it is hard i would say it is a calcerous algae, if it is soft i would say it is sponge