I have some dry compost, with no manure, and was thinking of mixing it with black sand for substrate. Will this work? I tested to make sure the soil won't turn the tank into a cesspool.
You'll probably want to lay the compost down first, and then cap it with the black sand to keep the dirt 'down.' That seems to be the normal approach, and that's what I did on my two 5.5's, and it works beautifully.