Cleaning Old Live Rock

[JaredL]

Bought this from a freshwater tank at LFS. It appears it used to be live rock in a saltwater aquarium. After having it in my tank for a year, I've decided I want to remove the purple stuff. Anybody have any good methods for doing this? I think it is Ohko(dragon) stone, but not sure. 

[Cory]

I'd try soaking in vinegar possibly. Thats how you can get rid of calcium deposits. 

[Andy's Fish Den]

The purple is what is called coralline algae, it's something saltwater and reef hobbyists strive to get on the rocks in their aquariums. There are companies that make "fake" live rock for the saltwater hobby and they also color the material they use to make it appear as if it is covered in the coralline algae. By looking at this piece I am going to guess that this is what you have, as most natural live rock has a lot of small holes and crevices, whereas this piece is pretty smooth. Now, someone could have taken a piece of rock and thrown in a SW tank and it grew, so what I would do is put some vinegar on an area, let sit for a short time and see if it softens it up that you can scrape it off.

[JaredL]

Been a few days of soaking in vinegar and scrubbing with a wire brush, but it got the stuff(coralline algae) off. Couldn't get in all the deep tunnels, but that was expected. Thanks for the help guys! Hope some color comes back after sitting in a tank for awhile.