After I had read the posts on the complex subject of "Earth", I decided to do my limited experience.
I mix well for 3 years (in Amorphophallus only 1 year) my plants Earth more or less strongly with the broken clay, which is sold in Aldi markets as Winterstreumittel.
http://www.discounterangebote.de/Produkt...nterstreumittelor even "overpriced" as Liaflor
http://www.liapor-shop.de/shop/article_1...aid%3D102241%26
Last February, you could evenly for €1 / 10l to buy, at the moment there are €2,5 / 10l.
You should flush it before, otherwise yellowish reddish brownish scum build up.
An acquaintance of mine has it in his shrimp Aquarium filter material and so far no problems.
This spring I planted then my first two konjacs in 50% DIY potting soil, 30% clay and 20% light coat of sieved compost.
The tubers have pretty good zugelgt, even though I have 4 times put the plants in the garden, because the site did not like me.
169 g-> 790 g + 80 g spin-off
211 g-> 930 g + 100 g spin-off
I have the impression that water is better absorbed and stored evenly and that solidified the substrate of less altogether.
Next spring I will make some tests with A.albus and A.konjac in different soils.