I use play sand and I love it but you have to RINSE IT, RINSE IT and when you think you're done RINSE IT SOME MORE. If you use black sand rinse it in a bucket you don't mind being discolored and do it outside.
My fish love it especially my cories and loaches because the sand's much softer on their barbels. I find it much easier to plant in as well. You need to stir it up every 8 weeks or so but in general I find it a lot easier to keep clean then the gravel.
I think Keyholes are fine in a 30 but I'm not sure about keyhole/cory compatability. You might wanna double check on that. They are South Americans but a lot of Cichlids are very protective of the bottom of the tank.