It seems as long as you have ADA aqua soil.. dwarf hair grass will grow and spread .. well plus 2+ WPG. I had some hairgrass that jsut lived, not thrived or spread out since May 06. As soon as I added ADA aqua soil (amazonia) it began growing runners and is starting to spread out. so.. you might wnna get amazonia.. since you are doing the amazon and all. but what do I know.. i have only had it for a few weeks.. but it is amazing stuff!