Sand is excellent but it does show up every tiny piece of muck and dirt. Good for cleaning I suppose but I do get a bit carried away and end up sucking some sand up too when i'm vacuuming. Looks lovely though when it's clean. I have really pale sand that looks white with the lights on. Maybe that's my problem! Ha! Hope someone can help you figure out how much. If you do go down the sand route make sure you rinse it really thoroughly. Once you think it's rinsed enough, rinse some more. There's some crazy amounts of dust in it that fog up your tank for a day or two before it all settles.