what is this on my live rock?

OK, that stuff is a bugger.

Lobophora variegata lobophora variegata - Google Image Search

(Please note that L. variegata is not a species name. Variegata is Latin for various or color-changing. Sometimes this happens because scientists are still trying to identify the differences between the species. Other times it happens because they are changing their minds on the nomenclature. Either way, the reason I'm telling you this is many of the different pictures shown above won't look anything like what you have.....but they are all classified as this).

The reason I wanted you to scrape it was because this was my first impression based on the picture.

Now, if you let it grow out for months and months, it could possibly be Padina sp. but I doubt it. Padina is called Potato Chip Algae.

BTW......many of the various types get even uglier as they get bigger.

 

you have 2 fire fish disapear, i think i read somewhere there tank jumper. look behind your tank.

 

lol going down right now

 

aww man.... so then i have to get my hands dirty and scrape all of it off? it really deteriates from the whole look of my tank. i never even heard of that name, no wonder i couldnt find anything on it