I just bought around 25lbs of base rock from the LFS. This stuff was all just in a bin in the corner of the store, it's very porous and will make great LR someday. My question is, is what is the best way to go about cleaning it before putting it into my tank? I've soaked them over night in the sink and then scrubbed them with a heavy bristle brush. There's still some "lichens" I think still on there but just wondering if I need to do any more? Any help would be appreciated, thanks.