Fluval bio stratum 2kg

is a premium, nutrient-rich, 1-3mm volcanic soil substrate from Japan, designed specifically for planted aquariums with delicate roots. It is infused with dormant, beneficial, bioactive bacteria that activate upon contact with water to rapidly reduce ammonia and kickstart the nitrogen cycle. 

I find this great to grow Alocasia corms in either in its own or mixed with perlite.