John, "By adding in oxygen either to the water column, or better to the substrate, it is possible to extend the life of the substrate because the BOD will assimilate the oxygen back into itself via bacteria (the biological filter), and this then becomes usable by the roots - typically in the same manner it does in organic farming techniques" And also - "My point was, as yours, you can keep a substrate going, and build it up, if there is enough new enrichment coming in plus oxygen to render the BOD reusable.." - But can I decide that my main fertilization method is through the water column and therefore I don't care too much about the substrate? - Is there any plant that must consume through roots in order to flourish? - How about cutting through the substrate with a knife every week in order to get more aerobic holes? - I know some of my hobby colleages are doing this, I do it occasionally but don't have enough experience to note a difference. - How about using snails for digging the substrate? Aviel. _______________________________________________ AGA-Member mailing list AGA-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/aga-member