Hi, I'm from Cairns. I'm also new here and I'm slowly setting up my 6x2x2
From what I understand, If you want discus to grow you will need to keep the water quality exceptional. If you do not need the fish to grow (adults), the water quality can slide a little.
It's not just detritus that lives in the sand bed, there is a whole universe of protozoans, fungi and bacteria in there. Some of which may be detrimental to discus, particularly if they're small.