38 Gal cube.
There's pagoda stone to make the sand higher in the back.
Some like this method for keeping the soil/sand cap away from the front, it can work for either method(rich sediment or not).
This tank is just plain sand throughout.
The water column is dosed once a week or two, a little bit and that's it.
SEA biotope for the most part. Water is a tad yellow form the wood, but activated carbon can be added to remove it.
Regards,
Tom Barr