Yes, both are for marine application....the "moon" is black, while the regular is......regular tan. I've found that most (if not all) black sands have a ferric component which makes cleaning your glass with a MAG type cleaner difficult. This ferric portion wants to stick to the MAG cleaner, potentially scratching your glass.
One is for freshwater and is filled with freshwater bacteria. You'd have to rinse it, dry it fully, and rinse it well again. Otherwise you'd just be adding a ton of dead bacteria to your tank.
Unless there is a significant difference in grain size, they're both black sands with maybe a few white bits mixed in.
Yeah, but when I say rinse, I mean RINSE. Otherwise you're starting off with a lot of dead gunk in your tank. The rinse for the sand itself is just to get rid of the dust. If you go for the freshwater stuff, you'd have to sterilize it. Or just accept that you'd have high nitrates right from the get go.
I can't tell actually. The first one seems like it's for freshwater. But it does mention marine. I can't tell just from the picture. If it's marine; it's good. If it's fresh, it's not.