THere is a link on here show me your Bare Bottoms or something like that. I am not a fan of the BB look, but one guy did something really cool. He took a type of Tile grout and paved the bottom of the tank with it. The stuff was very safe and he gave the name of it. It is available in different colours too, from white through brown, grey and black. It would be worth looking the thread up, it was very inexpensive also. I suppose you could grade it and add a few shells etc for a natural look.