From all my research, I've found that due to a nano's size, a buffering substrate like argonite wont really do much. Also since you need a low ph around 6 or so for the calcium to dissolve, it's not going to do you much good anyway. You'd have to have a dsb for any real effect and with a nano, that's not gonna happen unless you fill up a container with a lot of sand and use it as a sump.