Wow, that is looking very good. On initial layout, I thought it would look pretty good but the lush planting makes it look excellent. Like the pop of red in back as well, something usually not done in this style.
i have always wanted to do both aquasoil and sand but i have no idea how takashi amano keeps them from mixing over time. Shrimp seem to love to mix sand and soil around and after a few months you have a salt and pepper look lol. I have seen people use dividers with a hot glue gun but I still am not sure that will work