Don't get me wrong here, I do like southdown sand. But, the use of it or any dry sand in cycleing will take a bit longer than using live sand, it does work well but it takes time just for it to cycle too. AS mentioned, once they drop, they can drop almost overnite or they can take a few days, but normally it is much more sudden than you would expect.
Again, be PATIENT. Trust us, it is ALL WORTH IT!