Freshwater to Saltwater cross over ?

I have some what i would call barnicles that were given to me out of a freshwater tank. They have green algea on then that is hard to remove. I was wondering if anyone has a good way of removing it, and or if it will effect my tank since the algea is from freshwater and i am putting it into saltwater. I want to use them as they have many hiding places for samller things, but if its not safe then i will just throw them out or store them for use in a freshwater tank at a later date.

Thanks, Erik