Yeah, thanks for the input. I'm actually going to try and find a filter bag that will hold this stuff, going to have to be a small micron based filter and use it as filter media or perhaps put it directly in my sump/ref. instead of mud. It's becoming a popular medium for water filtration, especially if I can break it down to graphene properly.
Gonna be some trial and error I'm sure, I have a diatom filter sitting here, I may start testing with it's filter bag and see. I'm pretty certain it'll only be a benefit to my tanks if I can contain it!
I think it's generally too fine and light to be much use as a substrate, and that's just the physical aspects. I'm pretty sure graphite is relatively inert chemically, but not sure if there would be other sorts of issues with it reacting with stuff in the water/food/whatever.