I'd keep it natural looking just know if you add a bunch that over time all the sand will be on the bottom and the larger size gravel on top. If you only add a little into the mix the larger size will still end up on top but you can still see the sand in between the scattered gravel. I'm trying to go the Safe T Sorb route for my tank with a small grain nat6gravel on top maybe as a cap or just straight safe t sorb