Thanks Creekbottom. I think I'll skip the hunting down other options. My time is limited and its not worth driving around the city to save $10 (or whatever it might be). I'm not filling the tank, just topping off the substrate. But I'm glad to hear you did okay with the Exoterra sand.
Thanks exv152! I can't see the difference between Seachem Onyx Sand and Seachem Flourite Black Sand. Is it just a colour difference? Or is it more then that? I already have flourite black as a base, so I'm not sure its worth the extra nutrients to cap it too. Now if they sold half size bags...