there is no black patches, it is really just a dingy look. I have about 8 large hermits, that I am going to get rid of and get smaller ones, the large ones are too destructive and leave alot of waste. I am not sure what kind of live sand it is, I bought it from my lfs it was in a bag filled with water, but it was a real pretty white at first, and it is really fine. When I clean the tank and disturb the sand it will cloud the water for a little bit, hope this helps.