[Michiba54]

I haven't decided if I'm going to use the natural sand as final top layer yet. I'm afraid over time it might fall down through the gravel layer.

Haven't mixed the two myself, but from what I have seen of other people who have it will probably sink within a few weeks at the most.... and potentially look horrible depending on the sand/gravel ratio.

EDIT: I just looked at your pictures again and that is a pretty deep bed of gravel. Me thinks your sand would just disappear.

 

[Michiba54]

Do you filter your water through a DI filter too or just RO?