I have been doing some research on substrate. What I have found is called Stalite Perma Till.
Size 0 is roughly 1.5mm to 3.0mm.
Size A is roughly 3mm to 6mm.
Stalite is rotary kiln fired expanded slate heated to 2100 degrees F. It has 50% more surface area than typical gravel or sand.
Chemical Composition can be seen here:
Sterile and Inert.
PH of 7-9.
Durable, will not decompose or degrade over time.
Color is a vary dark gray when under water.
It comes in .75 cu ft bags (40 Lbs) for $9.00 each. In a 48x12 inch tank, one bag will fill it to 2 1/4 inches. 2 bags will fill the same size tank to 4 1/2 inches.
Compared to Flourite, it would take 3 bags of Flourite to make up .75 cu ft. (45 Lbs).
As you can see the weight of Stalite is very close to Flourite.
I received a sample yesterday and after rinsing, I am soaking it in some water for a couple days and then testing the water.
What I am thinking is putting a layer of peat with Jobes plant sticks at the bottom and then cover this up with Stalite.
Please let me know if you see anything that would make Stalite not usable in a fish/planted tank.
It has been used in Horticultural, Nurseries, greenhouses, Landscape applications, Bioretention applications, Root Bridging to protect and preserve existing tree root systems, Structural soil for planting urban trees, Structural soil for turf fire lanes, service roads, compaction reduction, Wastewater treatment, and Structural concrete, Masonry and Geotechnical applications.
Stalite web page is http://www.stalite.com/