Coconut coir does mold, but only if there's something for the mold to eat. This is true for most substrates that you could use though.
Good point as sand/grout has the capability to mold as well. I wonder how coir compares to traditional substrates. Maybe that'll be an interesting experiment to try after I'm tired of playing with agar...
Edit: I also wanted to add that I have ordered two Chinese formicariums (from aliexpress since I can't read the OP's links!). I don't have the links at the moment but one was a large acrylic nest with foraging box and the second was a small Omni-lookalike. I don't intend on buying these regularly, I just want to see how the quality and build compares.
Edited by Foogoo, March 16 2015 - 8:15 AM.
Camponotus vicinus, Crematogaster 1, Crematogaster 2, Formica francoeuri, *, *, Myrmecocystus testaceus, Novomessor cockerelli, Pheidole hyatti, Pogonomyrmex californicus, Pogonomyrmex rugosus, Solenopsis invicta