As I said in a previous post, I took a few years off of aquariums and apparently forgot some of my knowledge over the years. I remember years ago researching a bioactive substrate for aquariums but I can't remember anything about it. The tank would in theory pretty much manage itself with only topping off needed. Plants took a large part of the bio load, but I seem to remember something special about the substrate. Maybe introducing microorganisms or something into the substrate. Does anyone know what I"m talking about?