I currently have a 4-5" substrate of red flourite on the bottom and Soil Mater Select on top. It's working quite well overall. I picked up a 9 liter bag of ADA Aquasoil (Amazonia I - normal size) with the idea of perhaps creating little "pockets" of Aquasoil in the substrate to plant such plants as Tonina who might appreciate or need it's attributes. I've read that Aquasoil generally needs some cycling time due to leaching of ammonia. By doing what I'm thinking in such small quantities of a 72 gal tank cause any ammonia spikes and issues? (I know this is a "lazy" way to add Aquasoil for certain plants but I'm simply not going to rip apart the tank and re-do the substrate right now, nor want to incur the cost of replacing it all with Aquasoil)