Poor quality potting mixes

Gardening
1

I couldnt find any choice article/ tests about the different potting mix. I have bought a variety of basic and specialty mixes, which vary tremendously in quality and composition, though they all bear the australian standard logo on them. The latest from Bunnings, Basic potting mix has mould through it; on their own website most of the reviews dont recommend it. At least Bunnings still publishes them. I should have read them before buying 4 bags of them. Any thoughts.