Wow, okay. No paludarium then...that slightly worries me in regards to the false bottom however, since that fills with water...will it hold up to that?
As for the ABG, I would personally pick up some organic topsoil(Mine is Earthgro, it cost me around 4$ with tax for a bag about the size of my torso) and mix in 1-2 bags of ABG. As long as it's mixed well, it should basically be watered down ABG mix. I went with the approach of dropping the ingredients I couldn't find easily and cheaply.