Since our areas are different, I would suggest maybe check with clintbrown at the Perennials Forum, I think I remember seeing him post his delosperma plants when it is in bloom. He may have better suggestions for you.
I have used Super Soil palm and cactus mix or Black Gold, their soil mix is much better than miracle gro. But I still add more perlite or pumice in it as well.
I think the miracle gro mix will work for the tropical cacti variety, not the desert types ones. So it is important you identify what type of cacti you will grow in it. It did say in its product description on the link you provided it is for other succulents.
Cinta and ssgardener has provided you with their formula, both looks good. You have aquarium gravel, perlite and miracle gro soil, so less soil and more on the other substrates.
