whats growing on my liverock?

[gsw the future]

im new to saltwater and just bought an established tank with 100 lbs of live rock and some live sand . i was trying to make a cave with the rocks when i saw this purple stuff on my live rock. ive only had the tank for about 4 days other rocks have also changed color is this normal?
this is a pretty bad pic i took with my cell since i don't have a camera but hope to get one soon, its the bubble looking thing almost in the middle of the pic.

 

[jessed244]

Yes, I believe what you are describing is coraline algae, it is good algae. Most people want it. Do you have a pic to be sure though?? But i think thats what you are describing

 

[ibew41]

does it look hard or soft

 

[nycbob]

if its hard, it is coraline algae. if its soft, then red algae.