2 Quarts Fine Charcoal
A perfect light weight material to use in the place of a screen layer. Placed on top of the large charcoal to fill in the gaps and create a smooth near flush surface for the ABG to cover and fill on top.
When using fine grade charcoal instead of a screen the biggest benefit is to the bioactive and lanted tanks. Plants can be changed and roots will be able to come free very simply instead of ripping the whole base below the substrate up with the plant.