In the final stages of filling my recent 180g steal and am trying to decide on the type of gravel to put in the bottom of it. I have seen some black rounded gravel at one of the home depot type stores locally that I like. It is rather largeish at up to 1 3/4" in diameter. I don't think it will be out of scale due to the size of the tank but am told by a local that I need to use smaller gravel to promote bacterial growth. Any thoughts or suggestions are appreciated. Thanks.