Well...
Still haven't cleaned the sand-bed. But, just tested my water. Down to 10ppm. From 40ppm to 10ppm in less than a week. I did do a 20% water change, but I'm impressed at how fast the purigen is working.
Thanks for the tips. Hopefully I can keep this think less than 5ppm. I hear 0ppm I the goal, but I'm not kidding myself, I'm okay with 10ppm, but 5ppm is my current goal.