Hi barb-e
That's a very pretty tank you have there.
What fish are in there now?
I don't really recommend that kind of gravel, at that thickness, for corys. Since I just posted about sand/gravel in another place, I'll just give you the link here for starters:
http/www.fishforums.net/index.php?showto...p;#entry1813976
Now, about the betta with corys. I've found them to get along fine, but that's not all there is to it. Corys do best in well filtered water with water movement at the surface. Bettas do best in still water. In the long run, the betta will wear itself out in a tank that is set up for corys.