Lichen on lace rock unhealthy?

[Black Sails]

I just picked up a really nice piece of lace rock at the lfs. It has a lot of lichen on it(or so I was told). It's orange and green. It is slightly soft to the touch and smells bad. I boiled the rock and will scrape off as much of the stuff as I can. Will it be harmful to my fish? Does it pollute the water? Can it be injested? Does it continue to grow? None of my other lace rock had any of this stuff on it. I'm second guessing adding it to my tank.

 

[Guest]

It is slightly soft to the touch and smells bad. I boiled the rock and will scrape off as much of the stuff as I can.

Anything that smells bad is a warning sign. I don't really know what lace rock is, but here is my suggestion: Scrape, like you said. Then put it in a bucket of a bleach solution (1 tablespoon bleach to 1 gallon of water). Let it sit for a few days, rinse and scrape till it's all gone, then rinse it a ton more. put it in another container with water and a LOT of dechlorinator. dont put it in the tank till you cant smell the bad smell or the bleach anymore.