I would you to follow Vladimir's method religiously, there's no joking around with castings. Wash, boil(10-15min), then dry and dilute in a 50:50 mix with washed sand(sand from HomeDepot). Use between 4-8lbs of the mix, I would probably use 3.3:3.3lbs; then probably cover with Pure Laterite, and 2" of fine gravel(Bits of Walnut). I hope this helps...! 