So, I'm giving dirt a try.
The tank is a new 6 gallon (28l), I bought it to suit the rocks I picked up.
Some earthmoving equipment ripped this out of the bedrock at the little stream across the road. The smaller piece is actually a wedge that fits perfectly in another large piece, so it makes a really nice tunnel, but I'd have to do a cube.
There is a layer of pool filter sand, then building sand mixed with washed soil from my garden. Topped with a purple sand (I know, but the light in the LFS is very turquoise so everything's colour looks a bit off).
Ignore the little filter, it is just there to clear the water a little.
The other reason for the tank, is it is my first try at growing glosso.
I only got like 10 plantlets or so.
The tank is small so I'll probably hook up the ladder diffuser.