Hello, A few years ago, an old barn on our farm was demolished but a lot of the rocks weren't taken away so I gathered them to do some landscaping around the house. My father and I believe them to be granite, some with some speckly looking things in them and they are fairly clean. Would they be fine to use in my tank that I'm setting up in a month. What would be good to clean them with, or should I just scrub them hard. I also plan on boiling them all since they have been in the dirt for a few years. Thanks for any help.