C. ferruginea 'Sungei Kerait' was my first purchase of cryptocorynes with locality known , the owner was kind enough to pack 02 plantlets for me. That was in mid February 2008 then when I had not set up me emersed tank yet. I planted one plantlet in 'GEX' brand substrate (light green packaging) and the other in used ADA Amazonia + Aficana (50%:50%), both in mineral water bottles setup.
This species is quite an easy cryptocoryne to grow, the below shows their condition in early April 2008 after one and a half month of growth, the cryptocorynes in both bottles were already developing new plantlets. The growth rate for this cryptocoryne is about 1 leaf per month.
In my opinion, the one grown in GEX has a better growth than the one grown in used ADA (Maybe it is less acidic? Maybe it is looser and less compact?). The plantlets from the one grown in used ADA substrate seemed to be stuck in the substrate and never could grow out of the surface at all.
I already managed to re-pot 2 plantlets from the one grown in GEX instead into my emersed tank, one during end May 2008 (in GEX substrate again with 1/4 wonder-gro roots tablet, with the pot placed in a tub of water of neutral pH) and one during mid July 2008 (similar condition to the above, except that the substrate is changed to GEX mixed with 'Kotobuki' brand Dr Soil).