Another vote for Black Diamond. I just changed over my tank from Pea gravel to Black Diamond, and I am very happy.It just struck me that setting up this 170 means I am going to need at least 170# of gravel. Getting it by 20# bags from PetCo sets me at $150. Are there cheaper alternatives, that are also safe for aquariums?? I am being picky too... I want black rocks only.