>Unfortunately, there is no inexpensive commercial source for laterite. >Aquarium Pharmaceuticals used to sell laterite, but it seems to be no >longer available, so Dupla is the only source. Thiel Aquatech sells laterite for about $7 per (lb?, kg?). Also another company sells a clay based substrate additive called "Substrate Gold" I can't remember their name, but probably someone has heard of them.