ok guys, I have read all the post about this black diamond sand and see some like it and some don't, everyone has something to say about it but not one person mentioned the most Important part of it... it has a lot of fine pieces of metal in it!!!!!!!! I am using it myself in a few of my tanks and seems to be ok but it has oil in it that you have to rinse out very,very,very good.. you also have to run a very strong magnet through it when you are rinsing it to get the metal out of it... And for those who already use it and don't believe it has metal in it put a magnet in your tank and see what sticks to it!!!!