The main source of nutrients in your substrate are the result of bacteria, both aerobic and anaerobic, breaking down waste, therefore they are replenished if your substrate is capable of supporting the process, so I would have to disagree with you in part. Some substrates may deteriorate, others get better. I'm neither a perfectionist nor an artist, but I know that science is as much a part of this hobby as is technique, and I certainly haven't seen anything I would call deterioration in my tanks that would make me want to destroy a balanced system that I have worked hard to achieve, and the science supports my "technique" as it does anything Amano does. _______________________________________________ AGA-Member mailing list AGA-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/aga-member