I've found a couple of recipes for ABG mix, in case you want to try to duplicate it:

2 parts Ground Tree Fern Root
2 parts milled Sphagnum Moss
2 part fine orchid bark
(i cannot emphasize *fine* enough here, it's hard to find)
1 part sphagnum peat moss
1 part charcoal

Will you be planting your vivarium?