Schombo/myrmecos like to be left alone .. they will go through a 'shock' phase if they are repotted so know that you might not see any growth from them for a few months until they have set. I have mine in coconut husk medium. It's called KK mix from Kelly Corner's which consists of charcoal, perlite, airstones and coconut husk chips. What I like about the CHC is that it doesn't break down as fast as bark so you don't have to repot as often.
They can come from 2 different cultures .. either hot and dry or intermediate temps and wet. ( See the link - Question for Dorothy - in my last post) If it hasn't grown for you, you can alter it's watering schedule and see what the results bring. You can expose it to more light but I would do so gradually to allow it to adapt to the new intensity. If there are any negative effects from any changes you make, simply return it to the conditions you originally had it in.
I hope this helps